Garry's Mod

Garry's Mod is a physics sandbox with no objectives or win conditions. You spawn props, weld them together, and see what happens. Build a car, a launcher, a Rube Goldberg machine—whatever the physics engine will support. The toolset includes constraints like hinges and ropes, plus ragdoll characters you can pose. Play alone or on community servers where thousands run custom game modes daily. If engineering isn't your thing, you can mess around with character models instead. The game assumes you'll either bring your own goals or find them in what other players have created. It's a toybox, not a campaign.