I liked Ghost in the shell and Afro Samurai.
Elfen Lied for sure, I watched it 8 times and I'm probably going to watch it again as soon as I separate some time for that.
Second best is Higurashi No Naku Koro Ni, it's a horror anime, but it's not your usual horror thing, it's pretty colorful and funny most of the times, but then comes a lot of torture and killing and it gets very dark and violent. I love it because it shows a lot of the killer personality, sometimes you just like the villain more than the good guys, you can understand why they are bad and you almost approve their acts.
Right now I'm watching Saint Seiya Lost Canvas, Hellsing Ova series and Death Note. Death Note is probably the best out of them, but they are all great series.
As a fan of Heavy Metal, I cannot leave whitout telling you about Detroit Metal City, it's a short anime, with lots of heavy metal music and nonsense jokes. It's awesome and it's the funniest one I have ever seen. I recommend everybody to watch episode 7 first. I had to pee after watching it, I had laughed to hard for half an hour. And then I just watched it again and laughed my ass off another time.
Full Metal Alchemist
Grappler Baki 1
Grappler Baki 2
Ninja scroll and AKIRA the best
I like full metal alchemist. It caught me eye fast seeing that voice (which i think is tails from sonic adventure) coming out of the suite of armor.
Dragonball Kai - If you're a fan of DBZ you need to get this as its basically DBZ remastered, wide screen, new voice overs from original actors, all the filler cut out. FTW.
Other awesome anime from the top of my head: Samurai Champloo, Tengen Toppa Gurren Lagann, Trigun, GTO, Initial D, Death Note... and bleach + naruto are good disreagrding the fillers.
I have about 350gb of anime
I would have to say my favorite is Cowboy Bebop, but I just started to watch Initial D and Full Metal Alchemist and have been enjoying them so far.
Fist of the North Star !!