It isn't necessarily the amount of gore, but how it is represented in the game/anime/movie/whatever. Manhunt made me wanna puke, and that game's blood just disappears as a red haze, but the executions were so sickening I could never play it. Painkiller has some ridiculous violence with limbs flying all over and the walls and floors turning black with blood, but it's so ridiculous and over the top it didn't shock me. On the other hand, any of you who played Prince of Persia Warrior Within after playing the Sands of Time were probably just as shocked as I was to see the prince send limbs and heads flying with copious amounts of blood.