Games like Stack
Games like Stack include Garry's Mod, Portal, Totally Accurate Battle Simulator, BONEWORKS, and Hello Neighbor. We matched them by the tags players give Stack on Steam (3D Platformer, Puzzle, Sandbox, Strategy, and 3D): closest matches first, and among equally close ones the better-known games.

Garry's Mod
Shared: Sandbox · First-Person · Casual

Portal
Shared: Puzzle · 3D Platformer · First-Person

Totally Accurate Battle Simulator
Shared: Sandbox · Strategy · Physics

BONEWORKS
Shared: Sandbox · VR · Puzzle

Hello Neighbor
Shared: Sandbox · First-Person · 3D Platformer

Teardown
Shared: Sandbox · Physics · First-Person

Portal 2
Shared: Puzzle · First-Person · 3D Platformer

BONELAB
Shared: Sandbox · VR · First-Person

Bloons TD 6
Shared: Strategy · 3D · Sandbox

Moncage
Shared: Puzzle · Casual · 3D

s&box
Shared: Sandbox · 3D Platformer · Casual

Crazy Machines 3
Shared: Puzzle · Strategy · Sandbox

Gorilla Tag
Shared: VR · First-Person · 3D Platformer

Zup! S
Shared: Puzzle · Casual · Physics

Dorfromantik
Shared: Puzzle · Strategy · Sandbox

Buckshot Roulette
Shared: Strategy · First-Person · 3D

Human Fall Flat
Shared: Puzzle · Sandbox · Physics

PowerWash Simulator
Shared: Casual · Sandbox · First-Person

Quantum Conundrum
Shared: Puzzle · 3D Platformer · First-Person

Berry Bury Berry
Shared: 3D · First-Person · Physics

Liars Bar
Shared: Casual · 3D · First-Person

The Witness
Shared: Puzzle · First-Person · Colorful

Slime Rancher
Shared: First-Person · Sandbox · Colorful

Internet Cafe Simulator 2
Shared: 3D · Sandbox · First-Person