My two best. "I'm sorry, I'm allergic to bitching and moaning." Halo... Hell, once on all of them, and a few times in WoW. Usually when someone's bitching about how the game's bugged when everyone else is doing fine.
"Be back in ten, my mom's sending me to the store." Amazingly, I came back and the random pug of HoR in WoW hadn't booted me.
My friend, "I have to go, Karlie's taking me bikini shopping. She wants my opinion." It's happened so often he sounded depressed.
Random guy, "Sorry, my house just got broken in to."