Guitar, vox, and a little tiny bit of piano. I can make a few chords, and play some a few little melodies. I can generally play a short little piece, loop it in garageband, add another short little piece, and so on till it sounds like I know what I'm doing :P
I am kind of a jack of all trades, master of none. I am first and foremost a drummer but I can play guitar, bass, piano, keys, and sing. The breadth of knowledge really helps my making electronic music.
I also have a studio in my basement and am learning how to make the most of it.