The Gunslinger

The Gunslinger is a Gungeoneer added in the A Farewell to Arms Update. He costs 7 to play, and starts with the Slinger and the Lich's Eye Bullets. He is heavily implied to be the Lich before he became the master of the Gungeon.

How to Unlock
As The Paradox, defeat the Lich. This will launch the player into a new run as the Gunslinger. Go through the game again, travel to the Gunslinger's past, and complete the glitched Lich fight to unlock him.
 * He can be unlocked in Rainbow Mode.
 * He cannot be unlocked during a Blessed run.
 * If you are trying to unlock him you need to get the bullet that can kill the past

Story
The Gunslinger is conscious of the Gungeon's situation and knows what happened there after he mastered it. He realizes his goal is to revert all of this, by killing his future self, the Lich, stopping him from becoming Gungeon Master and stopping the Great Bullet from falling, which would prevent the creation of the Gungeon.

Past Kill
Traveling to the past takes you to Bullet Hell. Unlike other pasts, you keep your health and all the items you have gathered during the run, as if going to Bullet Hell normally. Everything is identical to normal Bullet Hell until the Lich boss fight.

Instead of fighting a normal Lich that has three phases, you fight 2 Liches simultaneously, similar to the Glitch Chest Boss. One Lich is normal, and the other one has the same visual effect as The Paradox. The Paradox Lich fires Jammed bullets and has increased health. Luckily, the Liches use only their first phase, and the player will win once both are defeated. The final scene shows the Gungeon as it looked before the Bullet crashed into it and the victory screen shows the Lich blocking the Great Bullet (a variant of the title screen), implying that time was rewritten and the Gungeon was never created, fracturing the timeline and turning the Gungeon into a paradox.

This leads into the events of Exit the Gungeon, where the now paradox Gungeon begins to crumble.

It is unknown what happened to the Gunslinger after he completed his mission.

Strategy

 * The Lich's Eye Bullets allow the player to have any synergy that a gun could have without needing the counterpart. For example, the player can have the Cactus and get the Cactus Flower synergy without needing Broccoli or Orange.
 * The Lich's Eye Bullets allow the player to be wild with any item or weapon that has Synergies, so the player doesn't need to worry about getting strong items for later portions of the run, and can use money for armor, keys, or ammo.
 * Many weak guns are now much more powerful thanks to his passive, e.g. Cactus and Flare Gun, since these guns have many significant synergies. As a result, the strength of many guns is different for the Gunslinger compared to other Gungeoneers.
 * It is especially beneficial for the Gunslinger to go to secret floors for more opportunities to pick up powerful weapons.
 * The Shop many times sells low quality guns that usually are not worth purchasing for other gungeoneers. However, the Gunslinger's passive can sometimes make them excellent options for a cheap price.

Trivia

 * Gunslinger was created on the side as art by Joe of Dodge Roll while the other developers worked on the main game.
 * The Gunslinger first appeared in the game files in the Advanced Gungeons & Draguns Update, but was not playable until the A Farewell to Arms update.
 * The Gunslinger's appearance resembles that of Clint Eastwood in A Fistful of Dollars. Considering how the Lich resembles Lee Van Cleef's character in the movie The Good, the Bad and the Ugly, who serves as the antagonist of the same narrative universe, further connections between the Lich and the Gunslinger being the same, one being bad and the other good, can be made. There is also a resemblance to Justice from Afro Samurai which ties in with the Number 2 being included in the game.
 * The time count shown at the end of the Gunslinger's unlocking run is the time of both runs combined.
 * The poncho he wears seems to be alive, since it has a face on it which blinks during his idle animation. This, however, does not change any of the gameplay.
 * This may be a reference to Dave of Dodge Roll declaring on Twitter that he will make everything in the Gungeon a mimic, the Gunslinger wearing a "mimic poncho" would make even the player a "mimic" by proxy.
 * When petting the dog the poncho will smile.
 * According to the description of Slinger, he became known as the Gunslinger because he literally slings guns at his foes once they run out of ammo.
 * His injured portrait during the Punchout fight with Resourceful Rat shows his eyes to be Bullets, suggesting he has been using bullets as prosthetic eyes even before he became the Lich.
 * The Gunslinger lacks an animation for missing the Resourceful Rat with a left punch. Doing so will instead show a right punch.
 * Unlike the other Gungeoneers, the back of his character icon (seen when selecting a character in the Breach) depicts a bullet resembling the Lich's skull.
 * A special rendition of the Lich's battle theme is played during the fight with the Paradox Liches, making it the second soundtrack in the game to feature lyrics next to the main Enter the Gungeon theme.
 * The Gungeon's appearance on the final screen of the Gunslinger's past seems to closely resemble that of a sword, possibly referencing one of Blockner's quotes, "The other dungeons me and Manny used to loot never had any guns. It was always sharp metal."
 * This also potentially implies that the Gungeon used to possess an affinity towards melee weapons, rather than to guns.
 * As the Gunslinger is technically the Lich before the great bullet struck and transformed him into the Lich, killing his past should be referred to as killing his future/destiny. This also means that the Bullet That Can Kill The Past can also kill the future.