Top 5 (6?)
1. Cowboy Bebop: It had one of the most fulfilling endings to an anime ever. That's a rarity.
2. FLCL / Outlaw Star: This is a tie. FLCL was just right time right place for me and Outlaw Star features the coolest weapon in anime ever aka The Caster.
3. Yu-Yu Hakusho: Came in during my Toonami phase and had such an awesome cast of characters. The Dark Tournament arc made this show for me.
4. Trigun: I loved the post-apocalyptic wild west setting of this show. Vash is a great main character and they managed to blow me away with the whole Wolfwood deal. Awesome show.
5. Great Teacher Onizuka: Coolest teacher ever. This is another show where I watched it in the right time and place so it's become immortalized.
Honorable mentions would include Evangelion, Gundam Wing, Dragon Ball (Z), Death Note, FMA, Case Closed, Zoids New Century Zero, ect. There are a lot of good series but very few great series because a lot of them just don't nail the ending.
