https://www.humblebundle.com/store/killing-floor
Free for a limited time (1day or so)
Enjoy

thanks alot

using free since 2009 lol

thanks mate, here is some cookie for you

Got it

Thanks dude, you the MVP!

Stolen links
I didn't find the free game on my own
Props to @ Elfing: for being slower than me to create a thread.