Osu - Osu is Music, Rhythm, Single and Multiplayer video game developed by Dean Herbert.
Uberchord Guitar - Get better on your guitar. Fast.
StepMania - Rhythm game for Windows, Mac, and Linux.
Justin Guitar - Over 750 completely free guitar lessons!
Clone Hero - Clone Hero is a free rhythm game, which can be played with any 5 or 6 button guitar controller...
Instinct - Guitar lessons that listen as you play along