In no particular order:
Hajime no Ippo (The Fighting in English, although the title totally means Beginning the Step and both refers to our protagonist's step-by-step growth as a boxer and is a pun on his name, Ippo Makanouchi).
Ghost in the Shell SAC (1 only, 2 was a bit disappointing)
Last Exile
Black Lagoon
Cowboy Bebop
Trigun
Black Blood Brothers (little young, but great villainess and good story)
Full Metal Alchemist, orig and Brotherhood
Samurai X OVAs 1,2 and 4
Claymore (though I long to fanedit the crap out of it, the story and characters scream for better direction)
Hellsing Ultimate