Obvious. The largest official game-group herder.

Payday: the origin. Literally.

FPS, more Tower-defence oriented, wave-based, SF based, indie-ish look&feel, challenging.

The best PvE hordes game prior to Payday series, FPS, story-based, concurrent but post-apocalypse story, 4 player characters, user-friendly world design

TPS, wave-based PvE, casual-gory game, fantasy, players can install physical traps. 1-2 players