Right now, Cryostasis for the PC (also known by some as "The Russian Bioshock", which is pretty spot-on). Very good game. A first-person horror game where your body heat acts as your health. If you get close to fire, you get warmer. If you walk on ice, you get colder. If you're cold, not only are you closer to death, but you also load bolt-action rifles more slowly, reload more slowly, walk more slowly, and can't jump as high.