Can't remember if there was ever a thread for this, but this is probably my all-time favorite music/rhythm game.
It's called Osu! and has some pretty great features. Basically you load a "beatmap" which can be anything from anime songs to 2013's top 100, or anything in between. People have made beat maps for just about everything that is even semi-popular. Then you simply play. The game is played using the mouse, and it's a bit hard to describe accurately. So I'll include a video.