When you think Doom, you think Demons! The Imp is the first enemy type you encounter after the zombie duders. The sounds of scraping, ripping and tearing heard in the darkness. That little demonic gurgle SFX plays from behind a door. Imp's really help build that creep factor.
What is your favorite or least favorite Doom enemy type?
I like the sound Barons of Hell make when they die. Finally killing them is satisfying. I also appreciate the audio cue for Lost Souls, although fighting them is less than pleasant.
I just encountered my first Arch-vile in Doom II and yup, I hate them as much as it seems everyone else does. I won't be offended if y'all give me tips.
I think my favorite enemy, both design and combat wise, is the Revenant. It's an enemy that immediately demands attention, both through it's scream and with it's absurdly dangerous guided missiles. But it's also a bit squishy so you cn take it out quickly if you get the drop on them. Plus, an angry skeleton with cybernetic armor and missile launchers is really cool.