Prototypes aren't usually something to get excited about, and we often only see them after a project has been cancelled (or when one shows up at E3). But a small group of indie developers have popped some footage of their project on YouTube, and hot damn is it a nice pitch.
At the moment, the prototype is called Towers. It's very much a living environment in a neolithic fantasy world, showcasing players running away from giant beasts, petting beasts, hunting, flying with handmade gliders, roaming around colourful lands, and just generally exploring.
Again, all of this is just a prototype built by six people over the course of a year. But imagine taking this as a pitch to a publisher or even saying to your friends, "Hey, look at what we put together, do you think this could be interesting."
I'd totally go some kind of MMO or larger action-RPG with this sort of vibe. There's not much more info on the official website, but it'd be fascinating to see this idea spun out a lot further.