The Humble Store is currently running a massive sale on shooters, including Killing Floor 2, and in order to get a bit more exposure they have decided to give away the original Killing Floor for free. So if you're interested, simply head over to the Humble Store and you'll be slaying vast hordes of mutants in no time.

I've personally spent over 300 hours playing Killing Floor, so if you're into team-based horde modes I would definitely recommend you check it out as it really is a great game. Killing Floor's visuals may be a bit dated by today's standards, but its weapons are still some of the most impactful and fun to use, so for the low price of "free" you really can't go wrong with Killing Floor.

On a slight side-note, I would recommend holding off on purchasing anything from the Humble Store until a bit later. The Steam Summer Sale is set to begin today, so it would be a good idea to first check out if there is any difference in price before cracking open your wallet. And finally, here's one of the more bizarre trailers for Killing Floor. Its for a Halloween update so there is a bit of a skin-swap on most of the monsters, but it should give you a good idea of what sort of nonsense to expect: