I've got an 18 for (insert ability here)
We get it, your awesome at a thing, which means that you probably dont mess it up, but terrible things must still happen.
Strength - you're too strong, and that door was hand carved mahogany. Good thing it was worth a hell of a lot more than whatever that goblin has hidden in his pockets.
Dexterity - You're far too quick and look at that you've gotten separated from the group. to bad your spastic ass cant pay attention to anything.
Constitution - You really dont feel that massive head wound? its probably fine, or it isn't and what was your moms name again?
Intelligence - Everyone understands perfectly, they just aren't sure why you had to be so condescending about it.
Wisdom - You're wisdom has detached you from the world, you start to see the pointlessness of whatever it is you're doing.
Charisma - you're hair is fine I promise.
This bad stuff happens on rolls of 18 instead of crit fails on 1's.