Alternatives to osu!

Guitar Hero clone

Kart racing game

Extensible rhythm game engine based on StepMania

Real-time strategy game

Frontend for emulators, game engines and media players (OpenGL graphics API)

Open-source transport simulation game

Arena-style first person shooter

Multiplayer online battle arena game

Game launcher with the ability to run Windows games

Audio player

Client for Old School RuneScape

Indoor cycling game