Inevitably the Zerg, for me. (Admittedly, I've only played Half-Life out of the rest of the list, but still. Zerg.)
Metroids
The Flood
The Zerg
Head Crabs
X Parasites
Phazon
Other, please explain
Inevitably the Zerg, for me. (Admittedly, I've only played Half-Life out of the rest of the list, but still. Zerg.)
That's more of a mild nuisance. I mean, they don't affect humans, but there are parasites that force their host to jump into a pond, then rip their way free while the poor thing's drowning (1), or force the host to climb a stalk and hold utterly still for three weeks, while it slowly grows out of the head before spraying out toxic spores, infecting every thing in the area (2). Or, maybe one that just attacks the brain, twisting aggression and kindness as well as attracting the host to cats, which it then infects (by making the host smell...delicious) in order to breed (3). Oh, wait, that last one does affect humans, as well as rats and cats.
EDIT: As for the one that most freaks me out? Guinea worm. In fact, I think I'll go post that one in Gare's thread.
Last edited by Mistral; 17th-February-2011 at 01:03.