Use brass knuckles to try and kill players/A.I (or other melee weapons which haven't been properly configured)
melee glitch: hold s (for block), and keep attacking
infected: aggro them first time, and they sometimes do a loop, or go a bit forward relative to you, then come back and start attacking you
infected in certain areas/scenarios, will sometimes stay still, and look at you before chasing you, (unless you look away from them)