The World Warrior. "Hey, hey, Street Fighter!/Keep fighting, make the future brighter!" The cool thing about this one is that, for the most part, all of the music is played by using sound-effects from the game itself. There are no drum-beats, just the sound of Bison being punched in the face.
A rendition of Final Fantasy V's Ancient Library. Just to be different, he did this song without the use of any instruments other than his own voice. But that doesn't mean that it doesn't sound like there are a bunch of instruments. He just did those sounds with his voice, as well.