If I put up a respectable score - "DDD". "D" is my first initial, and it's simply faster for me to just keep mashing start. My tendency to overnudge has unofficially branded "DD" as "double danger", but I maintain that it officially has no particular meaning. If there's 10-letter scores, I'll try to work "DDD" into some game-related pun.
If I get on the high score board with a crappy score (say, the high scores just reset) - probably just POO or SHT.