Favorite:

Angel Wing. Even though Rinoa (argh!) uses it.
Blue Magic. Most of them. All of them are good. Aside of Laser Eye, Gatling Gun and Eletrocute.
Quick Shot.

Least Favorite:

Duel. Argh.
...Laser Eye, Gatling Gun and Eletrocute XDDD
Hyper Shot, Canister Shot and Flame SHot o.o
And, Angelo, that would be WONDERFUL.... wuithout Angelo Cannon. Angelo Cannon is CRAP! And Wishing Star appears... what am I saying? It NEVER appears, I've yet to see its animation, really! And Invincible Moon... I've seen it four times, in 5 or 6 playthroughs x_x