At level 3 you learn to craft ammunition and repair damaged weapons quickly and with ease. As a Marksman you are proficient in in all crossbows (and firearms with the loading property if used), tinker’s tools and smith’s tool’s.
During a short rest you are able to create 5 new crossbow bolts using 5 broadheads, and 1 piece of timber. (Or you may craft 5 lead balls using a campfire, steel ball mold, and 1 pound of lead.) You may also repair one weapon during this time if you are in possession of the correct tools and materials.
Lvl 9 Sharp Eye Beginning at 9th level, you can easily gauge the battle strength of your enemies, and exploit their weakness. You gain Expertise in insight checks if you don't already have it.
At the beginning of an encounter you learn which creature is the highest CR, their AC, equipment in view, and best saving throw modifier.
Special Options of Attack: You can also target specific areas of a hostile target as seen below. You can use this feature an amount of times equal to your intelligence modifier. (minimum 1) You regain 1d4 expended uses of it at the end of a short rest (up to your intelligence modifier at max). At the end of a long rest you regain all expended uses of this feature (up to your intelligence modifer at max).
Sharp Eye DC = 8 + your proficiency + your dexterity modifier
Legs/ wings/ fins: When you choose this option, your next weapon attack has a -5 to hit modifier. If hit, the target must roll a constitution saving throw. On a failed save, it must spend 1d4 feet of movement per foot moved until your next turn, and takes damage as normal.
Torso: When you choose this option, your next weapon attack has a - 5 to hit modifier as you fire directly at the targets torso. If hit, the target takes full damage, and must make a strength saving throw. On a failed save the target is knocked prone.
Head: When you choose this option, your next weapon attack has a - 5 to hit modifier, however if it hits, the target must roll a constitution saving throw. On a failed save it has disadvantage on dexterity saving throws, and attack rolls for 1d4 of it's turns.
Arms: When you choose this option, your next weapon attack has a -5 to hit modifier. If it hits, the target must roll a strength saving throw. On a failed save they must drop whatever it is they are holding with their hands. If the target is holding separate items in each hand, only one hand must drop (shooter’s pick).
Lvl 13 Steadied Aim Beginning at 13th level, you learn to control your breathing before each shot.
If you do not spend any movement on your turn, you gain advantage on your first ranged weapon attack next turn. Alternatively you may spend a bonus action after moving only half your walking speed and ending your movement behind ½ cover to steady yourself, you may get this advantage next turn as well
Lvl 17 Keen Eye Beginning at 17th level, you may add 1d6 to your ranged weapon attack or damage roll when using a Sharp Eye attack option.
The Marksman Subclass for Rogue
Lvl 3 Craftsman
At level 3 you learn to craft ammunition and repair damaged weapons quickly and with ease. As a Marksman you are proficient in in all crossbows (and firearms with the loading property if used), tinker’s tools and smith’s tool’s.
During a short rest you are able to create 5 new crossbow bolts using 5 broadheads, and 1 piece of timber. (Or you may craft 5 lead balls using a campfire, steel ball mold, and 1 pound of lead.) You may also repair one weapon during this time if you are in possession of the correct tools and materials.
Lvl 9 Sharp Eye
Beginning at 9th level, you can easily gauge the battle strength of your enemies, and exploit their weakness. You gain Expertise in insight checks if you don't already have it.
At the beginning of an encounter you learn which creature is the highest CR, their AC, equipment in view, and best saving throw modifier.
Special Options of Attack: You can also target specific areas of a hostile target as seen below. You can use this feature an amount of times equal to your intelligence modifier. (minimum 1) You regain 1d4 expended uses of it at the end of a short rest (up to your intelligence modifier at max). At the end of a long rest you regain all expended uses of this feature (up to your intelligence modifer at max).
Sharp Eye DC = 8 + your proficiency + your dexterity modifier
Legs/ wings/ fins: When you choose this option, your next weapon attack has a -5 to hit modifier. If hit, the target must roll a constitution saving throw. On a failed save, it must spend 1d4 feet of movement per foot moved until your next turn, and takes damage as normal.
Torso: When you choose this option, your next weapon attack has a - 5 to hit modifier as you fire directly at the targets torso. If hit, the target takes full damage, and must make a strength saving throw. On a failed save the target is knocked prone.
Head: When you choose this option, your next weapon attack has a - 5 to hit modifier, however if it hits, the target must roll a constitution saving throw. On a failed save it has disadvantage on dexterity saving throws, and attack rolls for 1d4 of it's turns.
Arms: When you choose this option, your next weapon attack has a -5 to hit modifier. If it hits, the target must roll a strength saving throw. On a failed save they must drop whatever it is they are holding with their hands. If the target is holding separate items in each hand, only one hand must drop (shooter’s pick).
Lvl 13 Steadied Aim
Beginning at 13th level, you learn to control your breathing before each shot.
If you do not spend any movement on your turn, you gain advantage on your first ranged weapon attack next turn. Alternatively you may spend a bonus action after moving only half your walking speed and ending your movement behind ½ cover to steady yourself, you may get this advantage next turn as well
Lvl 17 Keen Eye
Beginning at 17th level, you may add 1d6 to your ranged weapon attack or damage roll when using a Sharp Eye attack option.
https://www.dndbeyond.com/subclasses/1825109-hitman
i made it into a homebrew class for gun