see, heres the problem...
NO!
thats all.
this won't work for one specific reason, timing. By the time you whip out your knife and stab at the dragoon, it has already pounced on your slow-reaction ass. The same goes for all the aliens. Speed is the downfall of humans. They just cant outrun the aliens.

. 'Sept for grangers. You may want to spend hours coding a knife so you can beatdown a granger.
When was the last time you saw someone knife an alien in any kind of game/movie/television show?
My point Exactly. Not that this isnt a bad idea!!! Someone may want to make a server where aliens have no attacks and have to try to survive a certain time limit. The humans could have knives only and must defeat the pathetic aliems.