Games like One Gun: Cat
Games like One Gun: Cat include Borderlands 2, My Friend Pedro, Undertale, DELTARUNE, and Bastion. We matched them by the tags players give One Gun: Cat on Steam (Action, 2D, Singleplayer, Loot, and Shooter): closest matches first, and among equally close ones the better-known games.

Borderlands 2
Shared: Action · Loot · Shooter

My Friend Pedro
Shared: Action · Shooter · Indie

Undertale
Shared: Great Soundtrack · Singleplayer · 2D

DELTARUNE
Shared: Singleplayer · 2D · Great Soundtrack

Bastion
Shared: Action · Singleplayer · Indie

Zombotron
Shared: Action · 2D · Singleplayer

Dust: An Elysian Tail
Shared: Action · 2D · Singleplayer

BioShock Infinite
Shared: Action · Shooter · Singleplayer

Cat Quest
Shared: Action · RPG · Singleplayer

ICEY
Shared: Action · Singleplayer · 2D

Borderlands 3
Shared: RPG · Loot · Action

Hollow Knight: Silksong
Shared: 2D · Singleplayer · Indie

Fallout 4
Shared: Singleplayer · RPG · Shooter

Pizza Tower
Shared: Great Soundtrack · Indie · Singleplayer

Wolcen: Lords of Mayhem
Shared: Singleplayer · Action · Loot

Hollow Knight
Shared: 2D · Singleplayer · Great Soundtrack

South Park™: The Stick of Truth™
Shared: RPG · Action · Singleplayer

It Lurks Below
Shared: Action · 2D · RPG

Terraria
Shared: 2D · Survival · Action

SurrounDead
Shared: Singleplayer · Survival · Loot

The Escapists
Shared: Singleplayer · 2D · Action

Hotline Miami
Shared: Action · Great Soundtrack · Indie

Grand Theft Auto V Legacy
Shared: Action · Shooter · Singleplayer

Geometry Dash
Shared: 2D · Singleplayer · Great Soundtrack