Its been awhile since I've watched anime so I can't really remember which one I liked the most. :(
Openings as in opening credits? If so, I go with Cowboy Bebop.
And The Boondocks, though not an anime, it is animated.
edit: didn't notice the "post clips" sorry
[COLOR="Black"]Excel Saga's episode 26 opening [url=http://youtube.com/watch?v=9Ibs_4blCNI&search=Excel%20Saga%20Opening%20song]FTW[/url][/COLOR]
I have too many, I'll narrow it down to three. -Not in order-
Bleach opening 3, High and Mighty colour. http://youtube.com/watch?v=rjz0JCUiAgk
Evangelion Opening, Cruel Angel (I think that's the name)
http://youtube.com/watch?v=EgATlhZFAfs
Trigun Opening..-Forgot the name, sorry-
http://youtube.com/watch?v=NzHe4U5c5Oc