Not an RPG, but an optional rule one may self-inflict upon themselves. I'll be trying something similar for an experiment.
The idea is simple: Before you make your post, consider your options. Then, roll your dice. The higher you roll, the more successful your character performs in your post. The lower, the more you will write him as sucking. The lowest roll means automatic fail, and the highest means automatic win.
For example, Let's say I wanted Joe to dodge a laser blast. Using two six sided dice, if I rolled a 2, then Joe would take the blast to the face and be launched into the stratosphere. Epic Fail. If I were to roll a twelve, however, then Joe would dodge the blast, use his amazing tai chi to redirect the blast, amp it up with his own fire magic, and launch it back at his opponent.
Most rolls will be somewhere in between, but the idea is to help gauge your character's awesome ratio- since they cannot do the perfect move all the time. I'll be testing this out for the next week, using my D20. Feel free to try it yourself, if you're up for a bit of random luck in your RP.
I'm not proposing a change in rules. This is an optional, self inflicted challenge, like a Nuzlocke Run. No need to be suicidal like me.