This paper model is an Adeptus Mechanicus Knight Paladin, a small combat walker of the Adeptus Mechanicus that is one-man version of a Titan and smaller than even the smallest class of true Titan, the Warhound-class Scout Titan used by the Titan Legions, based on the game Warhammer 40K, the papercraft was created by Newobmij, and shared by William Perry. There is also a Knight Paladin Titan Paper Model on the site.
Knights normally deploy in squadrons comprised of several of these war machines. The most common type of a Knight is about nine metres tall, with its head serving as the cockpit. Knights are the smallest and weakest of Mechanicus walkers, but they still are formidable and fearsome machines, all armed with an array of weapons beyond the power of even the strongest of Space Marines to bear.
You can download the paper craft model here: Warhammer 40k - Knight Titan Free Paper Model Download