My game is a space invaders/breakout style of game where you're a squirrel throwing an acorn to kill spiders.
https://itch.io/jam/gmtk-2019/rate/463448
This is maybe not a hack, but I decided to implement a combo system where you can earn extra points by killing multiple spiders before the acorn lands on the ground again, which will make the game a bit more dynamic. The implementation is simple: when the acorn collide with the ground, the combo counter resets to 0.
The thing is that it's possible for the player to pick up the acorn before the acorn hits the ground. But instead of adding extra logic to reset the combo counter when the acorn is in the player's hands, I thought it's better to leave it as it is. Then skillful players are able to stack even longer combos by catching the acorn before it hits the ground + I write less code. I saw it as a win-win.
Another "hack" I'm proud of is the clouds in the backgrounds. The clouds are actually based on the inside of a cylinder that rotates around the scene. Incredibly easy to implement, and I think it adds to the game.
Here's how it looks like in Blender:
