This paper model is a Hopper Mine, an anti-personnel proximity mine that hops into the air towards the target before exploding, much like a bouncing betty, from the video game Half Life 2, the papercraft is created by MooNFish.
These mines are carried and deployed by Shield Scanners. They are vaguely dome-shaped with three sharp "legs". When dropped, the mines use these legs to bounce around until they land facing up on a smooth surface. They then jam the legs into the ground, attaching themselves very firmly.
You may get this paper model template here: Half-Life 2 - Hopper Mine Free Paper Model Download