Hikari no Rock (the ending song from Bleach: The DiamondDust Rebellion) was a very awesome one, then there was Velonica by Aqua Timez, the first theme song of Bleach at the beginning of the series, and let's not forget High School of the Dead's opening!
My fave 2 Anime songs is Soul eater's 2nd Opening, "Black Paper Moon", and Dragounaut: The Resonance's only Opening, "Perfect Blue". both are mostly in Japanese, but they are great! I think i like Black Paper Moon more though, cuz its got the most english ive ever seen in a japanese anime song. I think the one line/s that hook/s me to this song is "Fairy blue kimi no tame ni, hoshi wo kudaki kazaritsuketa, Black Paper Moon, shijite kureta nara, When you're, lost "Here" I am, "Forever" with your "Soul".