Games like Gun in a Well
Games like Gun in a Well include Vampire Survivors, BALL x PIT, Halls of Torment, Skul: The Hero Slayer, and Dead Cells. We matched them by the tags players give Gun in a Well on Steam (Action, Action Roguelike, Arcade, Platformer, and Roguelite): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · Roguelite · Bullet Hell

BALL x PIT
Shared: Action · Arcade · Roguelite

Halls of Torment
Shared: Action Roguelike · Roguelite · Action

Skul: The Hero Slayer
Shared: Action · Action Roguelike · 2D

Dead Cells
Shared: Action Roguelike · Roguelike · 2D

Rogue Legacy
Shared: Platformer · Action Roguelike · Action

Spelunky
Shared: Action Roguelike · Platformer · Roguelike

Megabonk
Shared: Action Roguelike · Roguelite · Action

Hades
Shared: Action Roguelike · Roguelite · Action

The Binding of Isaac: Rebirth
Shared: Action Roguelike · Roguelike · Replay Value

Rogue Legacy 2
Shared: Arcade · Action · Platformer

Nova Drift
Shared: Arcade · Action Roguelike · Roguelite

Death Must Die
Shared: Action Roguelike · Roguelite · Action

The Binding of Isaac
Shared: Action Roguelike · Action · Roguelike

Risk of Rain (2013)
Shared: Action Roguelike · Action · Platformer

Dungreed
Shared: Action Roguelike · Action · Roguelite

Downwell
Shared: Action Roguelike · Platformer · Arcade

Soulstone Survivors
Shared: Action Roguelike · Roguelite · Bullet Hell

Brotato
Shared: Action Roguelike · Roguelike · Bullet Hell

BlazBlue Entropy Effect
Shared: Action Roguelike · Action · 2D

Enter the Gungeon
Shared: Action Roguelike · Bullet Hell · Roguelike

Star of Providence
Shared: Action Roguelike · Roguelite · Action

Nuclear Throne
Shared: Action Roguelike · Action · Roguelike

Super House of Dead Ninjas
Shared: Action · Action Roguelike · Platformer