Creeper World 4 is fun and not terribly long. It is basically a tower defense game, but instead of guarding a set path toy build towers to defend against, then push back, physics simulator liquid that kills whatever it touches.

Shadow Tactics: Blades of the Shogun, you play a small group of ninjas (and a samurai) in a top down stealth game. Takes place in feudal Japan and you assassinate your way through the plot.

Superhot. FPS with a weird plot about VR and a rogue computer program. The gimmick is if you stop moving, time stops around you (almost), allowing you to slow down and plan.

Lastly and is a game called Soccer Kids Alpha. It is literally the alpha version of the game so it is SUPER short. It is a turn based soccer game, but without the grid based system that some other games use. The alpha is great and we'll worth the very short time it takes to finish