The Beast & Wonder Man Vs. The Brotherhood of Evil

 Of all of the X-Men returning for Avengers: Doomsday, I am looking forward to seeing The Beast the most.  He was cool in X3, but we didn't get to see him in nearly enough action scenes.  Hopefully that will be remedied in this new appearance.

Nightcrawler Vs. Warp

This would be an interesting battle.  Warp probably may be a slightly more powerful teleporter, but then again Kurt Wagner has amazing acrobatic abilities as well, not to mention that awesome tail.  It's definitely a match up I would have like to have seen if X-Men/Teen Titans crossovers had continued.