I have a very bad addiction to tower defense games! My favorite one would have to be "Fieldrunners" on the iPhone. I've never played this TD game before - it's pretty good from what I've seen so far, but the music gets a little annoying after awhile
My sleep schedule is definitely odd as well. Weekends I usually go to sleep around 3am and wake up at noon. Weekdays are slightly more sane - I usually go to bed at 12am and wake up at 6:30am.