Body Harvest/YMMV


 * Demonic Spiders: The mutant in levels 1-3. It constantly tries to jump on you, causing an instant kill if it succeeds, or at least destroying any vehicle you're using. This is used as incentive to prevent harvesters from eating too many humans so that the mutant never appears. In contrast, the level 4 mutant has a better weapon, but is less of a threat because it hovers instead of jumping.
 * The stationary Alien Gunners in Java are no slouch either.