~deep breath~
Hellsing: best vampires ever, period. Both the sub and the dub of both of the series' are near enough perfect in the way they deliver their lines, the main character is possibly a god-mode stu, but he pulls it off in a way that's both believable and amazingly entertaining.
Black Butler: Victorian England with a kit with what is essentially satan as his butler. Just as badass as Mr Alucard from Hellsing. Little bit creepy at certain points, and the kid who's butler it is seems to get kidnapped twice a week, but well worth a watch.
Claymore: Superpowered girls with enormous swords, what more could you possibly want. It also delivers a fantastic and complex storyline.
Trigun: Another fantastic story, with lots of violence and some -very- cool guns. (see also, the Cross Punisher)
Fruits Basket: A little different from the others, more romantic than anything else, but the characters are engaging and the storyline is fantastic.
Ouran High School Host Club: as above
Air Gear: One of the few anime that i've actually got most of the manga for, great series with a good balance of humour and grittiness.
Black Lagoon: Mature series about modern-day pirates/smugglers, good amount of humour, plenty of drama, and a LOT of violence. If you want to avoid creepy there's a few episodes in the second barrage that you may want to steer clear of (those bloody twins... ~shudder~), but other than that, it's fantastic, and the third season is in the works at the moment. Also... Revy.
Escaflowne: Medieval Mecha anime, the first serious anime I ever watched. It's a pretty old one, and it shows it's age, but it's still really good.
Death Note, Gurrenn Lagann, some series' of Gundam, Bleach (although that's a hella epic) and The Melancholy of Haruhi Suzumiya are also all worth a look.
enjoy