I've been playing Warframe and while at first glance it seems so primitive it becomes apparent that's got so much more going for it. The maneuverability and button combinations, the weapon customization, the Warframe selections, the way it just opens up to you if you experiment.
It's still in beta, so it lacks a bit of polish but even at this stage it looks good. It's a lot of fun when you can get a friend (or three) to tackle the missions together. Playing solo is an option but it's not much fun unless you wanna stealth it, which is very difficult to achieve without the Shade warframe.