It's true, I have a knack for making comebacks in FPS deathmatches. I think it just comes down to getting my footing on a map or figuring which weapon works for me.
My favorite has to be a 15 kill comeback to tie Grant in Halo 2 at 22 or 23 kills and then fighting out those last two kills. I'm not sure who won that match, but it sure was a blast. There've been many games where I filled that gap and then lost but it sure is fun.