Beating a GM with the Morra Gambit!
The Morra Gambit is hugely popular at amateur level despite being regarded by "theory" as insufficient compensation for a pawn.
Grandmasters aren't supposed to lose against the Morra Gambit, but GM Viesturs Meijers (Elo 2479) of Latvia lost to Andreas Weber (Elo 1862) of Germany in the first round of a 7-round Swiss Open at the Bad Zwesten Chess Festival. Long live the Morra!
Because of the loss, GM Viesturs Meijers continued to play much weaker players than himself for the rest of the event and eventually took first place with a score of 6/7!
Game via TWIC.