One of the big changes in tabletop RPGs in the past decade is the concept of the hero point, also known as drama points. The hero point mechanic allows the player to something to spend to show that character is putting more effort into what he or she is doing. I estimate the first use of a hero point mechanic comes from Victory Games' James Bond: 007 RPG. The game also introduced villain points, a mechanic that allowed the GM to let a villain escape or even survive to go on to do even more villainous deeds.
Hero points are typically earned by the PCs for acts in-game and are then spent as needed. The points usually give a bonus on die rolls, either adding a large number (see various Cinematic Unisystem games, such as Buffy or Army of Darkness) or adding more dice to a die pool (see Force Points in WEG's d6-based Star Wars: The RPG or Edge in Shadowrun: 4th Edition). However, one game took a different route.
Superbabes: The RPG from Tri-City Games, based on the titles of AC Comics, had a mechanic called "Bimbo Points". Instead of earning and spending, players could take a Bimbo Point to succeed against all odds or two Points to do something outside the game mechanics. Naturally, there was a catch. As the Bimbo Points accumulated, the chance of a "Bimbo Event" grew. If the GM rolled the number of accumuated Bimbo Points or less on a twenty-sided die, an event would occur for that character, and the Bimbo Points would be erased. The event table in the game comprised of mostly embarassing situations, such as wardrobe failures or paparazzi infestation. The idea was to avoid discouraging players from taking Points while still giving them a reason not to take too many.
While the concept worked for the setting, it occurred to me that the idea could be taken and transposed to a different game without too many issues. The big catch is the name. "Bimbo Points" isn't exactly a great term to use. "Backlash" or "Karmic" might work better. The events would need to be changed, too. Here, though, I see the players being helpful, coming up with a number of ideas for the table. Give each suggestion equal weight on the table, and leave a roll of 100 as either a group event or for a chance of multiple events.
What sort of games would work with this? Right now, I'm still thinking it over. I suggest not combining Backlash Points with a system that already has a hero point mechanism; that's just overkill. Other systems work on the idea that the PCs are doomed, so being able to avoid, even temporarily, bad things works against the mood. (Call of Cthulhu comes to mind here.)
Classic fantasy, though, could use it. Sliding down stairs while firing arrows into orcs? Definitely outside most games' mechanics. Definitely worthy of a backlash mechanic. Using a whip to swing across a massive barroom brawl? Backlash point. Just remember, tailor the events for the game.