ugh, Ok, I'm gonna try not to go too overboard here:
Naruto:
Naruto vs. sasuke - my favorite fight from any anime for the most part
garaa vs. Lee
shikamaru vs. anyone
Sasuke vs. Oro
the 3rd vs. oro
...more from naruto but that's too many already.
One Piece:
Luffy vs. Arlong
Zoro vs. mr. 1
Luffy vs. Crocodile
Spike vs. vicious/Pierrot Le Fou/vicent --all awsome.
All the fights in HunterXhunter are great also. Particularly killua's fights
ED vs. Greed -- best fight in FMA no question imo
Saito vs. Kenshin
and Goku vs. Piccolo XD
Naruto:
Naruto vs. sasuke - my favorite fight from any anime for the most part
garaa vs. Lee
shikamaru vs. anyone
Sasuke vs. Oro
the 3rd vs. oro
...more from naruto but that's too many already.
One Piece:
Luffy vs. Arlong
Zoro vs. mr. 1
Luffy vs. Crocodile
Spike vs. vicious/Pierrot Le Fou/vicent --all awsome.
All the fights in HunterXhunter are great also. Particularly killua's fights
ED vs. Greed -- best fight in FMA no question imo
Saito vs. Kenshin
and Goku vs. Piccolo XD

guess what i'm trying to say is that not understanding an opponents technique, or not expecting a move, is no excuse for defeat, it just proves who the better swordsman is.Shishio didnt now Amakakeru fully (even tho he was helped by soujiro) and Kenshin didnt know Kagazuchi.So i fail to see that pt.