I rarely rage quit, but when I do, I ...
never mind.
Seriously though, I think I've only rage quitted once or twice in my life. I think both times, I didn't even say something. I avoid insulting my team mates or arguing with them as much as possible, even when I feel like it would be all within my right to tell them how much of a jerk their being. Insulting and arguing with "allies" is counterproductive 99.9% of the time (in my experience anyway). Rage quitting is even more counterproductive. There has been more then one occasion where I end up playing with just one other guy against 5+ opponents, and I have always fought the good fight. On rare occasions, I can even win such games, in which cases, I just feel sorry for the rage quitter(s).
But if I were to let my temper get the best of me... I guess I might say "Now you see me, now you..." and just quit the game.