A site like this
can help you find anime you'll enjoy.
You've already mentioned watching Code Geass
(swoon) and some others I like, so...
I've long loved Neon Genesis Evangelion
, and have rewatched it many times. After (or before) you watch it, definitely check out the Rebuild movies as well! The first one was excellent, and the second is one of my very favorite favorites. The next two movies are what I most look forward to seeing in the coming years.Baccano!
Yes, definitely. Great characters, and an intricate storyline that shifts between hundreds of years at times. A+ on all fronts. While the original Japanese cast is fine, I recommend watching the dubbing with the English cast -- lots of strong voice actors, and I find they better capture the feel of the 1920s setting. Durarara!!
Another keeper, for all the reasons already mentioned and more. I didn't think I'd enjoy watching the character development of a headless character so much, but... oh, I won't spoil things. Great series.
I very much enjoyed Darker than Black
. You've got two seasons, and the OVA finished last year, so there's a lot of excellent material. If you want to watch it chronologically, watch the first season, the OVA, and then the second season. I do wish the second season was as long as the first, but it's still really fun and action-packed.
Some other great shows: Xam'd
, Tengen Toppa Gurren Lagann
, and Monster
Also, since you mentioned zombies: It just started airing, but if you're in for a great zombie/parody comedy, Kore wa Zombie Desu ka?
has been hilarious so far.
I could go on and on, but that should be enough for now ^^