StepMania - Rhythm game for Windows, Mac, and Linux.
Mattermost - Mattermost is an open source alternative to Slack.
Osu - Osu is Music, Rhythm, Single and Multiplayer video game developed by Dean Herbert.
Cisco Jabber - Cisco Jabber lets you access presence, instant messaging (IM), voice, video, voice messaging, desktop sharing, and conferencing.
Clone Hero - Clone Hero is a free rhythm game, which can be played with any 5 or 6 button guitar controller...
Slack - A messaging app for teams who see through the Earth!