Hmm there's so many... but, of all fights, I choose:
-
Kenshin vs. Shishio - Rurouni Kenshin
-
Kenshin vs. Saitou - Rurouni Kenshin
-
Spike vs. Vicious - Cowboy Bebop
-
Spike vs. Vincent Volaju - Cowboy Bebop: Knockin' On Heaven's Door
TO BE ANIMATED!
That's all I remember by now.