Associate
The monkeys, the spiders and the Many from SS2. It was the sound that freaked me out, especially if you couldn't see them straight away. There was also a level where you had to retrieve something or other from a generic warehouse with crates and lifts with lots of robots patrolling - pretty scary stuff
The headcrabs in the (dark) air conditioning ducts on my first HL run through
The Barons at the end of the shareware level of Doom
The headcrabs in the (dark) air conditioning ducts on my first HL run through
The Barons at the end of the shareware level of Doom