Jeez it's been a long time since I've watched anime. I used to watch a bunch of it on adult swim in middle school and I quickly lost interest in high school but there are still some perennial favorites that still appeal to me.
Cowboy Bebop, Outlaw Star and Trigun were definitely my favorites (good choices btw Underground Heretic). All are very, very well written and have incredible immersion. I did see one episode of death note a while ago and while it wasn't bad or anything, it really didn't catch my eye.