Crumbling Colossus

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
When this creature attacks, sacrifice it at end of combat.

The List

Magic 2012

Trample (If this creature would assign enough damage to its blockers to destroy them, you may have it assign the rest of its damage to defending player or planeswalker.)
When Crumbling Colossus attacks, sacrifice it at end of combat.

If another player controls Crumbling Colossus when its ability tries to resolve, you’ll be unable to sacrifice it. It will simply remain on the battlefield.