Medal of Honour. The controls weren't very good but all in all it was an extremely fun game.
Singularity: I wasn't in the mood for horror when I got my mum to pick it up while she was out and of course the first couple of levels were horror, but it was a really good game.
Aliens vs Predator: I went into it with hopes dashed because of reviews. My friend bought it for me because I did a favour for her as I had been wanting it for a long time. I wasn't expecting much when I played it but after finishing it, I can safely say that it is awesome.
Final Fantasy XIII: People can guess why I wasn't expecting much.
BioShock 2: After the second half of BioShock being action, I wasn't expecting any horror elements to appear in BioShock 2 and after playing it I can say that I was right except for one encounter but that's not the point. It was action based but it was fun, and the multiplayer may have been almost deserted but it was a blast.
Resident Evil 5: Horrible reviews, demo sucked, turned out to be fun.
Dead Space 2: After playing the demo I was horribly disappointed (to the point where if I had not already preordered the CE I probably wouldn't have picked it up) but also hoping that was just a crappy part of the game and not only was the game friggin' incredible, that part had been changed and was actually fun.
Lord of the Rings Conquest: I heard it was a really mediocre game and while it isn't a rollercoaster of an epic campaign, I had a lot of fun in the short time I had it.
The Last Remnant: It wasn't interesting but I bought it anyway and while I didn't beat it, it was fun.