Well, right off, the last two lines are almost meaningless. 'I might beat you up, if I feel like it, but then again, I might not.' So we can ignore those except that the person in question is a combatant, or fancies himself or herself as such. The first two fit a lot of people, so we really only have to look at the people who are imitated and shy in the game.

Though Squall isn't imitated 'all the time' like the riddle implies, he can be irritating and he is certainly shy. He's my answer.