Here's a THQ classic that I mentioned a while ago. This game is the absolute scariest game that I have ever played. The best part about it is that it does not present itself as such. There's no motif of murder, psycic eminations, or some crazy whacko, in neither its ads nor its environment.
The game is set in the Chernobyl exclusion zone. It's a region that surrounds the Chernobyl Nuclear Power Plant that blew up in 1986, and (in this history) again in 2006. For reasons unknown, anomalies dot the landscape. These things mess with gravity, wind, electricity, or just light you on fire, for example. From time to time, anomalies produce fist sized objects called artifacts. Artifacts give properties to the bearer, like resisting certain elements, while weakening others.
The game begins with you falling off the truck, with a mission to go kill "The Strelok". You progress through the game by doing missions for other people, while gathering and selling stuff. Enemies and equipment are plentious. I got bogged down fast. Also, ammo has weight, sometimes a lot. At some point, you are required to go into underground labs to retrieve documents to figure out what the hell is going on. They are (almost) all dark, and the mutants get much scarier (which no one told you about). I remember playing through those parts being scared out of my wits, and I was literally shivering in my chair. No other game has done that to me.
Before you ask, yes, S.T.A.L.K.E.R. is an acronym: Scavengers, Trespassers, Adventurers, Loners, Killers, Explorers, Robbers. It describes the people in the zone quite well. Where a group of three or more STALKERs gather around a fire, they start talking (in Russian). One of them inevitably pulls out a guitar and plays it. It's one of the most well modeled and atmospheric elements of the game. Since I'm a stupid American who doesn't understand Russian, it helped drive home the fact that this is a foreign and strange land.
While the gameplay is FPS, there are plenty of RPG elements, but I would not say it is an RPG. There are missions and an inventory, and like a certain shock of the bio variety, it does not have any kind of skill trees or attributes. You can't change much in the world, even though there are several different endings. Dialog trees don't affect anything, aside from accepting or rejecting missions.
There were several bugs when the game was released, but they seem to have been fixed. You need to get into a habit of saving frequently, especially at first. It will autosave before you go into a new area that requires a load, but it takes at least an hour to get to the second area of the game. The game has several imperfections, but it reminds me of the first Mass Effect. So remember: F.E.A.R. < S.T.A.L.K.E.R.