I've seen all of the episodes (if you don't include the filler), and I think it's impossible to have just one favorite character. I have about three or four:

Byakuya Kuchiki
Ulquiorra Schiffer
Kisuke Urahara

Okay, I guess three at the moment. I like Urahara alot because he's like me in alot of ways (smart, funny, blonde, lazy, freeloader, etc.). Also, I don't really know why I like Byakuya and Ulquiorra so much, but those two are my top favorites.

EDIT: Anyone know where I can get the background music that's usually played when the Arrancar appear, which can be called "Arrancar Attack', or the background music that's played when Rukia attacks with "Tsugi no Mae"?

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Atheism
The belief that there was nothing and nothing
happened to nothing and then nothing magically
exploded for no reason creating everything and then
a bunch of everything rearranged itself for no reason
whatsover into self-replicating bits which turned into dinosaurs.
Makes perfect sense!