The ace of spades, A revolver that values trust more than anything. It is part of the four aces. The first weapon used by Clint Eastwood the wandering deadeye.
A revolver with infinite ammo. +3 on attack roles. 1d10+dex of piercing damage. (5th level 2d10) You have access to 3 magical bullets. 

"By experiencing both victory and defeat, running away and shedding tears, a man will become a man. It's okay to cry."

I am the ace(Gains access level 2)(1 charge)
-Roll a 1d20 if you get 1-5 you 1 shot your target. get a 11-15 you one shot the nearest being from your target.

Duel of the west(Gains access level 5)
-In a 1 on 1 you gain advantage to hit when you go first during initiative

I'm out(gains access level 2)
-You will be teleported 60 ft away in exchange you wont be able to use Ace of Spades for the day

I trust my allies(Gains access level 8)
-you get additional +15 ft of movement and gains advantage on attack rolls.

Magical bullets
Boo - (gains access at level 1)(6 Charges)
A bullet deal 1d8 of necrotic  damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).

Switcheroo - (Gains access at level 5)(6 Charges)
A bullet that deal 1d10 psychic damage. Damage increases by 1d10 when you reach 11th level (2d10), and 15th level (3d10)

Try me - (Gains access at level 3)(6 Charges)
A bullet that deal 1d6 piercing damage. Damage increases by 1d6 when you reach 6th level (2d6), adn 10th level (3d6)
DC Dex save if saving throw fails enemy will be stunned if succeed enemy will have half of their movement

It’s up to you to decide whether a character has proficiency with a firearm. Characters in most D&D worlds wouldn’t have such proficiency. During their downtime, characters can use the training rules in the Player’s Handbook to acquire proficiency, assuming that they have enough ammunition to keep the weapons working while mastering their use.

Notes: You have to shoot yourself with the gun in the head and survive., Range, Ammunition (Firearms), Reload, Sap