Best wedding disaster I've witnessed was my buddy's ex-girlfriend arriving drunk and late to the reception where she dirty danced with all the guys (myself included, she was filthy hot) and a gal and my buddy the groom himself, prompting the bride to storm onto the dancefloor where she took off her wedding ring and threw it at him, shouting that it was "over". Reality show scenes.
Thankfully it all obscured a pretty lacklustre speech by yours truly!