Ravenholm in Half-Life 2 the first time I played through was quite the scary experience, especially since I ran out of ammunition for all of my guns at one point and had to kill a pack of poison headcrabs and a poison headcrab zombie with nothing but a crowbar. Plus, I was wearing headphones, which probably didn't help make it any less terrifying.
Also, S.T.A.L.K.E.R.: Shadow of Chernobyl. Scariest game I've ever played, especially the underground research lab portions (made even more scary by wearing headphones, at 2 in the morning, in the dark... I still shiver just thinking about it).
Also, S.T.A.L.K.E.R.: Shadow of Chernobyl. Scariest game I've ever played, especially the underground research lab portions (made even more scary by wearing headphones, at 2 in the morning, in the dark... I still shiver just thinking about it).