This list contains the series that has openings I like/love, most of which has to do with the music. Aside from Night Raid 1931, where the art style of the OP's was quite interesting to me and the music was awesome too :P
List isn't ordered in any shape or form.
Series with more than one OP will be listed for the exact one I liked.
Nana OP #1 ; Phantom ~ Requiem for the Phantom OP #1 ; Durarara!! OP #2 ; Fullmetal Alchemist OP #2 ; Fullmetal Alchemist Brotherhood OP #1 #4 #5 ; Shakugan no Shana II #1 #2 ;