FFU

Kaze, and most of the Magun attacks (I liked em so much, I went so far as to create my own summons, going so far as to create the lines and different soils, and chanting them on a mic (Recording of course) xD
Makenshi and his Sword Dragon summons

Inuyasha

Sesshomaru and his acidic poison attacks (Ive only watched Season 1)

Tenjho Tenge

Almost all the fighting ive seen so far has been awesome, especially the Masataka vs Soichiro fight in Ep.2

King of Bandit Jing

When Jing merges with Kir, it looks pretty cool having Kir grafted to his arm with the wings and the head as an energy cannon