If by "silliest" you mean funniest move rather than worst move, you can check out this thread:
http://www.chess.com/forum/view/fun-with-chess/master-games-with-illegal-moves
If by "silliest" you mean funniest move rather than worst move, you can check out this thread:
http://www.chess.com/forum/view/fun-with-chess/master-games-with-illegal-moves
What is the silliest move ever made in a game between masters?