Mine would definitely be F.E.A.R. I only have the 2nd one (I know, I'm weird, I didn't play the first one before starting the seconds) and I love it but hate it at the same time. That game can scare the freaking crap out of me! But I love it because I have an insatiable love for horror/thriller :3 Another game I like is Amnesia: The Dark Descent, but I am having trouble with it haha, my laptop sucks at listening to me, and it usually freezes on this one part. But I love that game so much!