UltraStar Deluxe - A free and open source karaoke game inspired by the Singstar™ game, runs on Windows, Linux and macOS.
SpaceX Falcon 9 Lander - Try (and fail) to land Elon Musk's SpaceX rocket
Yokee - Karaoke to YouTube videos
SpaceVR - Explore space with Oculus Rift (pre-launch)
KaraFun - KaraFun is the best online karaoke. Over 35,000 karaoke songs, with studio quality, at home or on the go. Regular updates. Free demo!
The Size of Space - An interactive visualization of the universe