And Alien Vs Predator (Quake 2 engine I think it was) when you played as the Marine. Was one of the few FPS games where you could get hurt quite easily...
Hey, I didn't think of it, and I always liked it a lot. The first Alien vs Predator was the most genuine horror experience out there: played at director's cut with the marine, it was scary as hell and extremely tense without the need of scripted events. The sonar blips were damn slow compared to the aliens, and you had the clear sensation that they came out of nowhere even though the developers didn't cheat. Sadly the sequel isn't half as immersive.
Also having the infrared vision excluding the sonar was a real dilemma compared to the gun excluding the torch in Doom 3. ;)