I can't pick one!!
Bleach: (There's a few... And pretty much all with Ichigo. )
Ichigo vs. Byakuya (The one in the Soul Society for Rukia's rescue)
Ichigo vs. Kenpachi (Also, the one in the Soul Society for Rukia's rescue)
Ichigo vs. Ulquiorra (The First one. I haven't seen any of the others yet.)
(Can't really think of more at the moment.)
Inuyasha:
Mostly all of the fights with Sesshomaru and Inuyasha
Sword Art Online:
Kirito and Asuna vs. I think the fifth floor boss (I'm probably wrong since I haven't watched it in awhile)
Is This A Zombie?:
Amamu's (I don't think I spelt that right...) first or second fight as a magical garment girl. (That one's just because it made me laugh.)
I can't really think of more for the moment. So, if I missed your favorite fight go write it in the comments for me! And I'll see ya on the next day!