my favorite is Shelton Benjamin last year during his face run. It was Christian and SHelton on top of the stage talking to Regal (and I think Kozlov and Jackson). Shelton was trying to talk smack and stumbled over the same line twice and had to start over. priceless.
"...and thats why i kicked your leg outta your leg!" infamous owen hart promo...but now that we know he was such a joker, i wonder if he said it on purpose to try and make someone laugh and break character.