Gundam Wing, G Gundam, Rouroni Kenshin, Tenchi Muyo, Outlaw Star, DBZ, Escaflowne, Inuyasha, and Big O were all my favorites back around when I was a kid, still are.
As far as the recent times go there has been a lot of anime I've become addicted to, a short list would be:
Highschool of the Dead
Golgo 13
Ghost Hunt
Air Gear
Kaze no Stigma
Code Geass
Death Note
Kore Wa Zombie Desu ka
Lastly, Neon Genesis Evangelion.