Hellsing / Hellsing Ultimate are amazing.

Cowboy Bebop was good.

Trigun was thoroughly enjoyable.

Samurai Champloo was good.

Afro Samurai was good.

Claymore was good but suffered from DBZ syndrome.

Deathnote was ogod until the plot started to die, but the first 15 or so episodes are thoroughly worth watching.

Bleach was terrible in my opinion. The first few episodes seemed like they were going somewhere, but 140 episodes later, it's just DBZ rewritten in my opinion. The few good story moments there are get killed by the massive amount of filler the series has. No series should run for as many episodes as this bloated storyline has.

Elfen Lied was very good and quite enjoyable.

Black Lagoon seems pretty cool but I haven't finished it.

Berserk didn't really capture my attention.

Gungrave was bloody BRILLIANT until it fell too far into the fantasy / sci-fi line of things, but I highly recommend it regardless.

That's about all that comes to my mind right now.