Overload Dice! This one's inspired by Cthulhu Dark a bit... It can work with anything, I guess, but let's say we're focusing on magic now... On a roll that you really want to take, you can add extra Fate dice to your roll, of a different colour, and roll them all.
You take your normal 4dF's result, and add any pluses on the Overload Dice. The blanks are ignored. The minuses, however, indicate you strained or misused the resource somehow, and either the GM gathers Overload tokens on you, or throws out unrefusable compels that are relevant.