[Phalanx]

Agreed on the first 2 quakes.
1 was great...so atmospheric...for me, it was the first TRULY 3d fps I played, and at the time seemed to really draw me in much more. Very effective soundtrack, good amount of gore, and some real freakout moments (like getting dropped on the first shambler you encounter...), good stuff.
The second I didn't really find that scary, but very intense, really got the blood pumping with some of the shootout scenes, still challenging to get through.

Two that I played, not horror...that I found particularly scary, were
"ww2 GI", graphically not much better than, say, blood...but, there were so many snipers and ambushes...I guess you'd have to have played it to know what I mean, but you felt very surrounded.
Call of Duty - I've only played through the first one, but just how REAL it seems...the firefights are just fucked up and chaotic, the effects are great and the sound iss unbelievable, I've said this before, but on numerous occasions I played this one, I had to just take a break because for me, it seemed to get to me...kind've walked away from the game feeling a little shellshocked every time, it's a hell of an experience.

One called "shade - wrath of angels" freaked me out some...played like indiana jones meets evil dead. Very neat "jumps" and mindfucks here and there.

Nosferatu - the wrath of malakai was pretty cool, with it's oldskool "film" look, nice ambient sound effects and some very cool beasts and bosses. Otherwise,
not that much of a great game, but could fill you with a sense of impending doom.