Chivalry medieval warfare is pretty good fun, steep learning curve but I like it.
It can be really frustrating or really satisfying, for me I'm usually like 3:1 kd at least so I really like it, but it still should be fun as a newcomer.
Aside from that, stuff like L4D/GMod I guess. Torchlight 2 is really fun too, but you might not be into that type of game, it often goes on sale for 8$ ish, same with Chivalry.
Free games like Warframe, TF2 also might be fun.