Fuck yeah, the invisible dudes. I was going through the Agroprom mission, stalkan my way through the basement. After killing the bandits, I made a sneakier attempt on the soldiers. I thought they were in the next room, but after preparing a bit, they had moved on somewhere. I snuck across the boiler room and saw their flashlights in the hallway. I got out a grenade and prepared to ambush.
Suddenly, that weird snarling noise I had been hearing for a minute became very very loud, and I saw the air distorting and shadows moving. Moving fast. Holy shit. I get swiped across the face, panic, and throw my grenade at my feet. Luckily, I dived just far enough behind a column that I wasn't killed instantly, and the shadow reeled a bit from the blast. He managed to get another swipe on me while I fumbled my sawed-off out, and gave him two in the face.
I stood there frozen in shock and pride for a second, then I got shot by the soldiers from the hallway who heard the commotion and came running. I still wasn't quite dead, dived back behind the column, and shot Combines in faces with my AK, as they came around the corner one-by-one, climbing over each other's heads Three Stooges style.
It's a pretty awesome game. I still remember the cold and empty feeling I had when I went back by Fox's shack, after tag-teaming bandits and mutants and soldiers with him like a half-dozen times, only to find he'd finally met his match with a pack of blind dogs while I was away. Poor guy.