If you're a fan of asymmetric multiplayer and games that really push the FPS concept to its very limits, you might be interested in Natural Selection 2. In simple terms, its a fast-paced multiplayer shooter that has aliens face off against space-marines in an all-out war. You'll need to construct buildings, defend territory, upgrade your arsenal of weaponry, and naturally, obliterate anything not-you shaped in order to secure victory.
Since trying to comprehend all of this is no simple task, especially if you've never played Natural Selection 2 before, allow me to show you one of the most recent gameplay trailers. While it won't give you a detailed look at all of the mechanics and tactics, it should at least let you know what NS2 is all about. Have a look:
If this sounds like something you might be interested in, you're in luck as Natural Selection 2 is completely free-to-play on Steam for the next two days. And for those of you that end up getting addicted to biting people in the shins with speedy little aliens, you can grab Natural Selection 2 at a 50% reduced price for the duration of this promotion.
Whether its worth checking out or not, that's a difficult question to answer, and not because Natural Selection 2 is bad. On the contrary, I firmly believe that NS2 is a great game, but the learning curve is absolutely monolithic! I've played it for well over 30 hours at this point and I'm still nowhere near competent with the majority of the weapons and aliens, though you might have a bit more luck as I was still fairly new to competitive FPS games back then. In other words, if you decide to grab Natural Selection 2 make sure you're aware of the fact that the name isn't just for show - the gameplay is ruthless and only the strong will survive!