Fallout 4 Gunslinger Build

+ indicates where you should use the You Are Special book.
* indicates where you should spend 1 perk.

Use the special book and 2 levels to bump your strength to 2, endurance to 2, and luck to 8, then collect each of the bobbleheads throughout the game to get to a final build of 3-4-3-6-7-9. Save your perks as you level if the perks below aren't available. Read the optional perks section below to understand why 11 LCK is in parenthesis.

Stength Perks

Armorer - Level 4

Ballistic weave makes this worth it. It offers 80+ physical and energy resistance (30+ is base, 110+ is level 4) on two armor spots for a total of 160+ physical/energy resistance.

Perception Perks

Locksmith - Level 3

This perk allows you to explore the Commonwealth, get more loot, and help you build your relationship with most followers.

Endurance Perks

Toughness is not worth the five points if you consider the strength and armorer logic earlier. 5 points into toughness gives 50 damage resistance, where 1 point into strength and 4 points into armorer gives at least 80, but more than likely 160 physical and energy resistance. That's effectively 32 levels spread evenly between Refractor and Toughness if that was possible. Ouch.

Life Giver - Level 3

More hit points means less dying (and less loading screens), especially early on when the hit point algorithm isn't very friendly. Slowly regenerating health over time is awesome and will save you a bunch of stimpacks.

Charisma Perks

Generally speaking, charisma gives you a bunch of experience early on through speech dialogs, so you aren't wasting too much by putting points here. The five points (and bobblehead) gives a settlement population cap of 16 and enough charisma with the help of clothing to pass just about all of the speech dialogs and get a bunch of caps in the process.

Cap Collector - Level 2

Nothing to see here, just perks for settlement building.

Local Leader - Level 2

Again, settlement building perks. Supply lines make building new settlements much easier and building shops and crafting benches makes your settlements pretty handy.

Settlement building is also a pretty good source of early experience. And besides, you're not really playing Fallout 4 if you aren't spending some time building settlements.

Intelligence Perks

Medic - Level 1

For settlement building only. The additional 10% stimpack bonus is worth a magazine, so it's not terrible. Save the stimpacks though, food is a better source of healing early on (and cooking food gives you a decent amount of experience early on).

Gun Nut - Level 1

For settlement building since the turret is really good for defense. Somewhat useful for early game weapon modifications, but you're better off buying weapons from vendors and moving the mods to the weapons that you actually use.

Hacker - Level 3

Just like the Locksmith perk, this allows you to play the game. You're going to find terminals that you're going to want to unlock, this makes it happen. It also has a minor impact on settlement building.

Science! - Level 1

Pretty much just for settlement building, mainly for the best power generator. Allows you to get mod scopes onto your weapons if you want that.

Agility Perks

Agility increases the amount of action points, so this build caters slightly to a sneaky/stealth attack playstyle.

Gunslinger - Level 5

Specializing in hand guns will make your life a lot easier. The increased damage is insane and hand guns are ideal for this build because of the lower AP cost in VATS works very well with Four Leaf Clover.

Untested variations of this build use Commando (for wounding legendary weapons) or Rifleman (for a long range sniper build).

Mister Sandman - Level 3

Arguably optional, it's in a pretty convenient place for this build. This perk offers conditional increased damage and you find a surprisingly high amount of sleeping enemies.

Action Boy/Girl - Level 2

Increased AP regeneration means more time using VATS and more time sprinting.

Ninja - Level 3

Ninja offers a substancial increase in situational damage and works well with Mister Sandman. You need to sneak to make this perk work well, but it's too good to pass up.

Luck Perks

Even though pretty much every luck perk is useful, the bottom part of the tree is the most powerful.

The biggest thing to note on the luck perks is that Mysterious Stranger and Ricochet are left out. The proc rate on both of the perks are pretty low and in the case of Mysterious Stranger, it can proc and still miss (and that is horribly frustrating).

Better Criticals - Level 3

This build lets you crit a lot. Every third or so shot should be critical, so the increased damage is welcomed.

Critical Banker - Level 3

Another perk that makes your crits more useful and the third tier effect is crazy good. This will allow you to crit four times without having to recharge and will let you take down deathclaws on survival difficulty easily.

Grim Reaper's Sprint - Level 3

This perk pretty much gives you 100% uptime on your VATS. Even on the hardest difficulty, you'll be one-shotting (OHKO) a lot of enemies so this turns you into a killing machine.

Four Leaf Clover - Level 4

This perk is bonkers. It procs all the time and it works with Critical Banker.

Optional Perks (and beyond 50)

If you follow the build to a T, you'll have two perks to spare on the road to level 50. You can always round off Locksmith, Cap Collector, or Hacker (in that order) if you want, but there are probably better options.

SPECIAL Stats

Using those two points to cap luck at 10 before you pick up the bobblehead is probably the best option; this trick will give you 11 base luck. This is the recommended place to spend the two perks (just make sure you do it before picking up the luck bobblehead!).

Agility would be your second best choice (although Gun Fu is rather impractical) unless you want to spend points 51-60 on getting Concentrated Fire from the perception tree.

Bloody Mess

This perk is probably the safest perk (although least interesting) to spend the extra two points and spending a third point somewhere along the way or after level 50 is completely reasonable. The 4th point isn't necessary.

Lady Killer/Black Widow

Another free boost to damage, but a little more complicated than bloody mess. It's also much better if the Sole Survivor is female. You get the 15% increased damage earlier than Bloody Mess, but since you have two spare points, that's pretty much irrelevant.

Gun Nut/Science!

Even though it's only recommended to put one point into each perk, more points into these perks means less time shopping and more time playing.

Using the less time shopping, more time playing logic, a point or two into Scrounger is another option.

Scrapper

Scrapper makes salvaging much better and makes weapon modifying a lot easier. I'd rather just pick up junk, sell my weapons, and buy junk from vendords (especially after you build vendors in your settlements with the second level of Local Leader).

Awareness/V.A.N.S

Some people say these perks are 100% necessary, but they are really just quality of life perks. They make the game slightly easier to play, but experience trumps the perks and the points can be spent elsewhere (especially if this isn't your first playthrough).

Equipment

Weapons

Righteous Authority/Lucky legendary prefix

Modify this weapon into a handgun and it should be your primary weapon.

The legendary prefix Lucky offers the same ability. Ideally, you'll get a 10mm weapon with the lucky prefix so you can get a silencer to take advantage of the Mister Sandman perk.

Deliverer/VATS enhanced legendary prefix

Deliverer is a very strong weapon for this build. It has a silencer, so it makes Mister Sandman relevant and you can buy the weapon modifications from Tinker Tom instead of having to craft them yourself.

If you get lucky, you'll get a VATS enhanced legendary weapon and you can mod that instead.

Two shot/Powerful/Freezing legendary prefix

Two shot and powerful are both better per shot weapons so they are slightly better when building up critical attacks.

Freezing is very powerful when you have critical hits built up and need the crowd control, so this prefix is very powerful against bosses or other very strong enemies, like death claws.

Wounding legendary prefix

The wounding prefix is probably the strongest legendary weapon prefix in the game because the damage stacks over the bleed period.

If you get lucky and find one of these weapons early, you can replace Gunslinger with Commando and modify the weapon to an automatic handgun.

Armor

For quality of life while playing the game, I highly recommend pocketing your armor for increased carry weight until you get rank 3 of armorer, then switch your gear to ultra-light for (10+ AP on your chest, 5+ AP on arms). Custom-fitted allows for better sprinting, while sleek offers better movement speed while sneaking, on your legs if you don't want the additional action points.

Military Fatigues

Your under armor clothing of choice should be military fatigues. You get 2+ AGI and modify them with ballistic weave for a bunch of resistances. Make sure you carry 2+ CHA clothing with you (ideally, you'll have Agatha's dress or Reginald's suit for 3+ CHA)

Minutement Outfit  for 1+ PER/AGI or Green Shirt with Combat Boots for 1+ CHA/END both get notable mentions.

Battered Fedora

Your hat of choice is the battered fedora because it gives 1+ LCK and can be modified with ballistic weave. You can substitute with the newboy cap or trilby hat for 1+ CHA as they both get ballistic weave, but charisma doesn't offer much in the game (although it is good to carry in your inventory for dialog checks).

If you want to give up a lot of resitance, Destroyer's Helmet sold by Penny Fitzgerald in Covenant gives 1+ CHA/INT or Commando's Helmet sold by the Brotherhood of Steel's Teagan gives a 10% reduction in action point costs in VATS.

Patrolman Sunglasses/Welding Goggles

Any 1+ PER eyewear will do because 1+ CHA eyewear doesn't offer any advantage for adventuring.

Liam's glasses gets a nod as an honorable mention with the 2+ INT bonus for the slight experience boost but shows up a little too late to be relevant.

Lucky/Cunning prefixed legendary armor

Lucky (2+ LCK) is slightly preferred because faster crit build up means more damage, but cunning (1+ PER/AGI) is nice for increased accuracy and more action points.

Powered/VATS enhanced prefixed legendary armor

Both make your VATS better. One or two of each of these on your equipment somewhere with the powered prefix (increased AP regeneration) being slightly better for sprinting, while VATS enhanced (10% reduced AP cost) is better for combat.

Sprinter's prefixed legendary armor

Increased movement speed is always nice. Fill out your gear with this.

Companions

Sprint to Diamond City and get Piper as early as you can. Even though she's unrelated to this guide, her companion perk is very good for leveling and she's easy to befriend with lock picking and generally being a good person. She can also be romanced then left at your main settlement for the Lover's Embrace perk (good for a 15% increase in experience gained).

Hancock - 20% increased Critical Meter Fill 

Hancock's Isodoped perk will make your critical meter fill 20% faster when you are radiated at least 250 and it's pretty much absurd for this build. You're going to bank a critical shot every 2-3 shots with this perk active.

MacCready - 20% increased chance of headshots in VATS

More hits in VATS means more crits and more crits means more damage. Even though shots to the torso or limbs are sometimes more effective, if you can get a headshot 80% of the time versus a torso shot 90% of the time, the headshot is going to be a better choice.

The slight increase in accuracy also allows you to save your critical attacks for when you need them and you can risk headshots on weaker targets while saving your critical attacks.

Deacon - 20% increased sneak attack damage

Stacking damage for free is a good thing, and Deacon synergies well with Ninja and Mister Sandman.

Variations

As this guide mentioned earlier, there are slight modifications that can be made to the build that leads to different gameplay.

Party Boy/Girl Variation

If sneaking isn't your thing, the Party Boy perk offers an interesting option. Take two SPECIAL stats away from agility, skip Ninja and Mister Sandman and put one point into Charisma, three point into Party Boy/Girl and spend the extra four points somewhere else (Bloody Mess comes to mind).

The main problem with this variation is that outside of the 3+ LCK from Party Boy, alcohol doesn't add much besides the temporary carrying capacity boost and charisma bump for dialog checks (it's easier to drink than it is to change your clothes).

Commando Variation

A slightly more versatile option, replace Gunslinger with Commando if you have a wounding legendary weapon.

Rifleman Variation

Replace Gunslinger with Rifleman. Overseer's Guardian is the best early-ish game weapon for this variation.

VATS enhanced prefixed legendary armor is now more important than the powered prefix and cunning is preferred over lucky.

Mod your arms to get Stabilized for better scope stability.

One could argue that perception is better than luck for this build and there will be a new guide that option.

Notes, caveats, and bugs (contains spoilers)

In regards to bobbleheads, they can be a pain to collect.

1. The endurance bobblehead requires level 18 because you need to pick a lock, so you will not be able to get Life Giver until then. Save your perks!
2. The questline to get the charisma bobblehead can get bugged. The bug makes it impossible to get the bobblehead with a console command.
3. The agility and luck bobbleheads are in somewhat high level areas; you may want to sprint through the area to get them (or turn the difficulty down).

You need to avoid murdering the Railroad until you get ballistic weave. It's pretty much game breaking if you skip ballistic weave on higher difficulties.