Burst Angel: is pretty good. Think slightly futuristic western...
Claymore is nice. I hope is comes Stateside so I can buy the series.
X is good, but by Clamp...
Rurouni Kenshin: it's an oldie but a goodie.
Samurai 7: based off the classic film Seven Samurai.
Avenger. Made by the .Hack group, and has the same feel. The sub characters tend to make the show funny.
Solty Rei: It has humor and is serious. Moderate to low fan service.
Elfen Lied: Just beautiful. It's short, being 13 episodes.
Gunslinger Girls: nice relationship circles and the beginnings of love...
Magic Knight Rayearth: Oldie, but a goodie.
Utawarerumono: looks nice, but I have mixed feelings. (probably because I watched it when I was majorly sleep deprived.)
Vampire Hunter D: Bloodlust: 'nuff said...