Games like Monster Masher
Games like Monster Masher include Vampire Survivors, Cookie Clicker, Skul: The Hero Slayer, The Binding of Isaac: Rebirth, and Megabonk. We matched them by the tags players give Monster Masher on Steam (Casual, Action Roguelike, Puzzle, Point & Click, and Roguelike): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · Roguelite · Casual

Cookie Clicker
Shared: Casual · Incremental · Idler

Skul: The Hero Slayer
Shared: Action Roguelike · Roguelike · Roguelite

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

Megabonk
Shared: Action Roguelike · Roguelike · Roguelite

Dead Cells
Shared: Action Roguelike · Roguelike · Roguelite

Astro Prospector
Shared: Casual · Action Roguelike · Roguelike

There Is No Game: Wrong Dimension
Shared: Puzzle · Point & Click · Casual

(the) Gnorp Apologue
Shared: Incremental · Idler · Casual

Shelldiver
Shared: Casual · Incremental · Idler

Hades
Shared: Action Roguelike · Roguelite · Roguelike

Death Must Die
Shared: Action Roguelike · Roguelite · Roguelike

Click the Button
Shared: Casual · Incremental · Point & Click

Timber Rush
Shared: Casual · Idler · Roguelike

Unpacking
Shared: Casual · Puzzle · Cute

Dungreed
Shared: Action Roguelike · Roguelike · Roguelite

Halls of Torment
Shared: Action Roguelike · Roguelite · Roguelike

Nodebuster
Shared: Casual · Incremental · Idler

Digseum
Shared: Casual · Incremental · Idler

Rocket Rats
Shared: Action Roguelike · Casual · Roguelite

Sephiria
Shared: Action Roguelike · Roguelike · Roguelite

Is This Seat Taken?
Shared: Casual · Puzzle · Cute

Enter the Gungeon
Shared: Action Roguelike · Roguelike · Pixel Graphics

Papers, Please
Shared: Point & Click · Puzzle · Indie