Mad Monkey Falls Down
Rule number one is that you will fall down if you are struck. So just fall down and skip being struck.
Grandmaster Training 21,000 gp
Utility Power Encounter (Move Action)
Effect: You shift up to your speed and fall prone at the end of that movement. If the next melee attack you make this turn hits, you can push the target 1 square and knock it prone.
Published in Dragon Magazine 404.