Ok, so there are two power concepts that I run across a fair amount in my fantasy reading, but that I have yet to figure out a good way of incorporating into the game.
1: Supernatural Luck: You know the concept: A character for whom everything just goes right. He can walk through the middle of a gunfight, and all the bullets just happen to miss him. He goes out for a walk and happens to trip over a briefcase full of money or the crucial piece of evidence to solve the mystery. His car never breaks down, he never gets caught in the rain, and even the birds always miss him.
Now, obviously this would be easy to implement by just giving a character loads of Fate points, but that feels a little too easy. I want there to be a catch to this power, some way in which relying on your power to tip the scales of Fate can come back to bite you. The best idea I've had so far is that taking this power also gives you an Aspect along the lines of "dependent on luck" or "weird luck", and that you cannot buy off Compels related to that aspect.
2: Inhuman Vulnerability: Taking things one step beyond the Catch, this is the case where not only do your powers offer no protection against a threat, but you are far more vulnerable than a human would be. For example, a lot of werewolf stories feature the idea that a werewolf is so vulnerable to silver that the slightest scratch from a silvered blade is death, and even touching it can burn. At the lower end, I imagine you could implement this with a "power" that gives certain attacks extra shifts of strength against you. For the higher end, I'm considering a rule that says that you can't take Consequences to buy off damage from whatever you're vulnerable to. You can still take stress hits (fluff-wise, because stress generally represents strain and near-misses rather than actual harm, crunch-wise because that keeps it from being quite so crazy brutal), but if someone actually lands a hit, they're taking you out.