I don't get freaked out or disturbed easy, either, but I am notoriously jumpy. The typical process I'll go through is: poker face, poker face... poke–OHMIGOD!!!! ... So that'd make me jump from a 2 to a 4, lol.
If it's a game with a lot of high-stress situations (a la the original Doom or Resident Evil 4 & 5), I get panicky, curse, stand up, jump up and down, etc. It's pretty funny.
Gee, I haven't played a game in, like, forever (ife's too busy), but now I'm gettin' a hankering to dust off one of the Resident Evils. Hmm...