Well, a particularly mean one would be: "Whenever the target fails an attack roll, they have a 10% chance to be subject to one of the following effects," followed by a list of effects normally used for critical fumbles. Mainly because critical fumbles are god-awful.
Then, you have things like: "The target takes a -X penalty on all attack rolls, saving throws, and skill or ability checks. In addition, whenever it fails an attack roll, saving throw, or check, it takes 1 point of Constitution damage." The Constitution damage can be replaced by anything bad, really. Lost actions are a good candidate for the slot.