I'm sure you've all thought about manhacks, those terrifying red-eyed razor-blade drones from Half-Life 2. Maybe you thought about how awesome their design was, or how useful their real-life implementation could be. Well, guess what? They exist now! 
 
Some fine gentlemen at the GRASP Lab, at the University of Pennsylvania have created the "Aggressive Quadrotor," an autonomous (yeah - hands free, not remote controlled) flying nightmare, that somehow gives off a sound more ominous than the Half-Life manhacks. Basically, these guys tell the thing the general path that they want it to follow, and then it tackles any obstacle in the way to get there. Throw a hula-hoop at it? It will literally time itself so that it can pass through the ring without bumping the edge. 

"Wait! I don't wanna waste the battery! I wanna throw it from the front-lines into a house full of terrorists!" 
Well, sure thing. You can kick this thing like a soccer-ball, and - just like the manhack - will adjust itself mid-air to full stability. 
 
But hey, I'm not one to tease people about such things, so here's a video of it getting ready to fly through some warehouse windows and cut up some rebels: