Probably the Stu-Pid Riding ones.

http://www.youtube.com/watch?v=IK8-fe9_LQY
http://www.youtube.com/watch?v=Sv75bCm7lZs


This is a favourite too, was watching it last night and think its class.

http://www.youtube.com/watch?v=bLz7U44xvCU

I THINK* its either Andy Gallagher or Possible Charlie Shaw, they are the only two people i've seen go backwards through that hairpin and get out the other side Quality clip.