I’d say Bleach (Asterisk), DNAngel (True Light) , and the 4th Full Metal Alchemist op (Rewrite) .
Gundm SEED Destiny 1: Ignite. \m/
I have to say my favorite is FMA fourth opening:Rewrite
Shaman King 1st OP (Oversoul)
Man, I got tons.
Uh…
Slayers-Megumi Hayashibara-Get Along, I guess.
Record of Lodoss War TV- Miracle Sea. The best part of the whole series right there.
Also, Logos Naki World from Hellsing is great. And Bleach’s one is also great.
Tsukuyomi Moon Phase (neko mimi mode de)! Vampire catgirl pwns!
Also Jungle Wa Itsumo Hale Nochi Guu (Love Tropicana), it’s the only music from an anime that I have on my harddrive.
The opening from Outlaw Star is my number three.
Need I say it? Oh right, this is the other forum, where I’m not well-known and well-thought-of. XD
- Saber Marionette J (Sucessful Mission)
- Saber Marionette J Again (Hesitation)
- Saber Marionette J to X (Proof of Myself)
Not in any particular order. They’re all tied.
Four words: Azumanga Daioh. Sorimimi Cake.
Rensai wo hanasaimasu
Giunka wo haiway ni aturereba
Ueno atsu wo…toki
Reuntachi machi ni
Kasokuzu habi wo aturereba
Ueno atsui ni…toki
Gikikikiki wo something merodii
Fushigi wa ototoberu
Oero hanasanai ii
Mune wo wo something SEVENTH MOON
…oewowowou
…doko ni wo tsubeteworekozaa
Mune wo wo something SEVENTH MOON
Wo dekuru ni atsu ni
Giunkezekurutachi
…tasuketa
Oooooh. I like Hellsing’s opening a lot, but I would have to say my favorite is Trigun’s.
Shell
Shell!
Shell. 
I also liked the first opening from FMA (Melissa) and the third one (UNDO) better than the others.
Also, Read or Die’s main theme and eX Dream from X TV both rock.
Naruto’s 4th opening, GO!!!
Bleach. And Ah! My Godess.
Couldn’t stand the bleach opening itself however it was an interesting OP.
Tenjou Tenge OP for it characters dancing
Kannatsuki no Miko just cause it has great music.
Elfen Lied for its use of nearly only still frames.
There are a lot of really good or interesting OP’s out there. Hard to really nail just one.
Record of Lodoss War - Kiseki no Umi (Sea of Miracles)
Full Metal Alchemist - READY STEADY GO!
Ghost in the Shell - Inner Universe
All good.
The second Naruto op
excel saga
witch hunter robin
Anything JAM Project ever did (Shin Getter vs. Neo Getter, Soultaker, Mazinkaiser)