Sanctum 2 (native on Fedora 21 Linux)
Channel: Rob Crowther
Date: 2015-07-28

Sanctum 2 is a Tower Defense/FPS hybrid with online co-op for up to four players.  An interesting combination of strategy and action (watch me suck at both in this video!) and works well on Linux, grab it now in the HumbleBundle Tower Defense Madness sale for less than a quid.

https://www.humblebundle.com/store/p/sanctum2_storefront