Favorite: Goka Mekkyaku, and it's not even close. A combo CD, the fattiest of fatty fireballs (BLMs don't @ me), and Kassatsu→Chi→Ten→Goka Mekkyaku on a big group is the ninja weeb dream.

Least Favorite: Meisui. It seemingly exists only to justify the fact that the Ten Chi Jin single-target sequence ends on Suiton, and that's not a good enough reason to have a whole button.