Rogue Trooper. I still don't know why I bought it.
But I'm not wondering because I think it's a bad game, quite the oposite. I enjoyed playing it 3 times, wich is a lot for a shooter these days (but then again, it is kind of old). It's just that honestly can't tell what makes me like it. The gameplay is nothing genius, graphics have their moments like any game, nothing more, perhaps a bit less... story is a bit deeper, but nothing that would knock your socks off.
I guess it will always be on my mind.
On second thought, rome: total war. I liked the way it looked, but the strategies, controls and all... it's way to much for my uncomplicated rush-in-and-see-how-much-lives way of managing a battle. And I knew I would feel this way before I bought it, because I saw it at a friend and thought exactly that.