Come on, we all know we accuse each other of this behind each other's backs with others...so why not we come out to admit publically the elements we are aware are "Mary Sue"-esque or Peter Pan-esque. Failing that, have a think about what elements are, and post them up...
For example, your character being a direct copy paste of yourself, or having a 10 inch dong when you've got a 4. Lol. Or being impossibly nice in every single situation with unflinching emotion.
I'll start...
- Anette is one. She isn't a Mary Sue per se, but my character having a young, beautiful and blue-eyed daughter is. Her existence is wish fulfillment in that regard, though their exact relationship and interaction I distance from myself, and attempt to make it as distinct as possible (rough 'n' tough dad versus elegant, well-spoken daughter)
- The look of Rhea. Busty, voluptous, red hair, full lipped, blue eyed? Yes please...
- Seriphyn's self-consciousness and timidity in the presence of certain women. Sometimes getting teased or flirted with, he does not react with a self-confident or cocky manner, instead sometimes he ends up blushing or otherwise going meek/sheepish. That said, this area of RP (romance, sex etc.) is the most susceptible to being a direct RL->RP copy+paste from my experience, as most other areas of him are different.
Phoneticizing an accent goes a LONG way to separating yourself from your character....for example.
Me (OOC) - "yeah dunno tbh. i think we'll see"
Seriphyn (IC) - "Yea', don't 'ave a fuckin' clue to be 'onest with you. Guess we'll just 'ave to wait and see, I s'pose"