I used to play a lot of Maplestory when i was younger. It's an MMORPG that's free to play and makes money through mostly cosmetic items. But it's changed so much since I started that it's almost a completely different game now. I'll sometimes play during their big events for the nostalgia. lol
outlast deluxe edition is available for free from humble bundle a free account is required to claim the game. This site has free games often and really good bundles if you don't know about it yet it's definitely worth checking out.The offer is only available for one more day.
War Thunder is a pretty cool ww1-ww2 era combat flight simumlator.
Dirty Bomb is an overwatch type game but free.
Heroes of the Storm, it's a MOBA like LOL and DOTA, but unlike LOL the cummunity is a lot less acidic (they also communicate less though)
Paladins is a fps style moba game.