Suffer, mortals (small dramatic pause) as your pathetic magic (small dramatic pause) BETRAAAAYS YOU!
I'm a mage, and 70% of the time I was the one to get the associated debuff, making this phrase that much more annoying.
BOOOOOOOOOOOOOOOOOOONESTOOOOORRRRRMMM
Yeah, he got easy enough to kill real quick, but when ICC was fresh and everyone was just slightly undergeared, we had to hear this one a LOT.
Virtually anything your WoW character says to you to let you know that it can't be done. Yes, I know that spell is on cooldown, I'm mashing the goddam button so I can use it as soon as it's OFF cooldown.
Virtually anything the disembodied voice says in Starcraft 2 when you don't have enough minerals/gas/supply, with "You must construct additional pylons" being the worst offender.