Best ever "best man" (using the term VERY losely) tale I ever heard was from a squaddie friend of mine.
It began....
"I'd love to be the first to announce that the bride and groom will soon be starting washing nappies"... Ahhh....says the audience..
"aye..not for a baby or owt but just that the dirty slag has been taking it up the shitter for so long now her arse muscles have completely packed up"
Cue bride running out the room crying and groom knocking best man out and beating him to a bloody pulp...
You've got to love squaddie, jock squaddies from the parachute regiment take foulness to a whole other level though