* GoddamnedBats: Rollerrats aren't particularly dangerous to a properly-equipped player, but they have an aggro range seemingly a mile long and their damage type (chemical) is usually not well protected against by most types of armor meaning that while you're at minimal danger of any serious damage, the chance of you getting away without taking some scratch damage is pretty low even if you're just running by.
* ThatOneLevel: Pandemonium, with Sector 42 coming in afterwards.
* WoobieSpecies: pretty much all the mutants, but especially the [[OurZombiesAreDifferent Biofreaks]]
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