What is the worst thing you experienced, saw, had to participate in, deal with, fix at a wedding where you were a guest or member of the bridal party?
One outdoor wedding we attended had everyone bring potluck - it was about 80 degrees out with no heating/refrigeration. Half the guests got food poisoning the next day.
At another, guests brought unruly kids who basically trashed the place. The parents decided "someone else would look after them" and proceeded to drink heavily. At the end of the night one parent decided it would be a good idea to lock all the kids in the women's bathroom. This was after they stuck their hands in the cake, got into the chocolate fountain and wiped that all over the linens.