In order: 1. All of Mayuri's fights.. (Seriously. I can't choose. However, I think Szayel vs Mayuri is probably my favourite.. XD) 2. Kenpachi vs Nnoitra 3. Grimmjow vs Ichigo 4. Starrk vs Shunsui 5. Kenpachi vs Ichigo
3. Kurosaki Ichigo vs. Ulquiorra Cifer (Round Two)
4. Kurosaki Ichigo vs. Grimmjow Jaggerjack (Round Three)
5. Shuuhei Hisagi vs. Findor Calias
Now, my reasoning behind my fifth choice is simply the animasi involved. It escapes me why they decided to put so much work into that fight of all the other options they had, but it sure did turn out great.