Duke Nukem II/YMMV


 * Goddamned Bats: Several:
 * The small spider creatures that latch onto Duke (some even fall from the ceiling) and drain his health until you shake them off
 * The slug-like creatures that throw their eyeballs at you, then explode into a shower of eyeballs when you kill them
 * The ships that fly overhead and drop bombs with a rather huge blast radius; if you don't have anything besides the default weapon you're practically guaranteed to get hit (and even if you shoot the bomb as it's falling, it blows up anyway and the explosion will probably travel downwards far enough to still hit you)
 * The panther-like creatures made of green slime
 * The small ships in the first level of episode 2 which don't appear until you're practically on top of them
 * The hopping one-eyed robots.