This is a tough one to answer as there are many shows that i like, though thinking about it i would have too say a tie between 3 shows i grew up with thanks to the cartoon network gold moment that was Adult Swim (All of them dubbed):
1. Cowboy Bebop: This is what classics are made of. This was one of the first mature Anime's i saw when growing up (before was watching stuff like Pokemon, One Piece, Toyko Mew Mew, etc), i was hooked on Cowboy Bebop while it was on air and loved every part of it. The Characters, the settings, the music, it's all so superb and holds a place in my heart as classic.
2. Trigun: Another classic to me that i love so much. The characters again make it so enjoyable (Vash and Wolfwood being the best ^_^) and i liked the setting of a futuristic apocalyptic like desert plant. Music was also kick arse!
3. Orphen: This ones a bit under the radar but like the other 2 mentioned above, i got hooked onto it on the Adult Swim block. For a fantasy Anime it's quite entertaining and has some good quirky comedy. It had a pretty good story too which gave an interesting insider to 2 of the main characters. Although the second season went down a notch, i still consider the first season to be an entertaining show in the Fantasy category.
Special Mentions:
1. Spice and Wolf (A Fantasy show that's more than what you would expect, great characters and lovely artwork and music. Had a great natural sounding dub)
2. Black Lagoon (My favorite action Anime that just simply kicks arse and has a delightful dub along with it
)
3. Baccano! (Defiantly a show that deserves more praise than it gets, Baccano! is like a massive barrel of fun filled with explosions, crazy characters, catchy music and superb dubbings.)
4. Soul Eater: (Made the shonen genre feel fresh again. The concept of weapons crossed with humans is facinating and the characters are very likable and entertaining (special mention to Death The Kid) and while it did have some of the usual Shonen cliches'it managed to do the impossible by making them seem less stale then they would of been. Art work is also very nice to look at, almost like a Tim Burton Halloweenish look to it. Dubbing was also well done.