Rock Lee vs Kimimaro and various fights from Tengen Toppa Gurren-Lagann, but I only choose tengen cause I love the style.

Goku against Freeza is epic

itachi vs sasuke nice very nice

agreed!

also, i never get tired of chun-li vs vega in the SF2 anime

Karas: The Prophecy opening fight scene redefined how I define an awesome fight scene in an anime.

However, Neon Genesis Evangelion Unit1 vs Zeruel will always have a special place in my heart.

the fight scene in ROD the tv and ova........historical man with extraordinary-ability......the girl who can slice ppl with paper (she rarely did it).....the woman who can walk through wall (can she dive through the soil??)......american special-force army (rambo......) .......the powerless british leader who had special leadership........all these made a good (classic) fighting scenes.......

The Matrix has fight senses down

train vs creed (black cat)
ruuji vs zairin (zoids genesis)
kenshi vs shishio (ruroni kenshi)
kira vs raww kira vs athrun (gundam seed)
kira vs shinn ( gundam seed destiny

also.....
saber vs assassin (faye stay night)
heero vs treize (gundam wing)
orochimaru vs jiraiya&tsunade (naruto)
gaara vs deidara ( naruto shippuden)
...... etc.

Naruto and Suske