This is one of the most brilliant conversions of this guy that I have seen. It is very straight forward, recognizable, and made of easily available parts. Looking at this guy you know it is Ku'Gath. The parts involved appear to be a Corpse Cart, a base or two of Nurglings, a Great Unclean One, vomit from a River Troll, an Chaos Sapce Marine Nurgle Icon, and a few bits and bobs (a small kettle piece, and what appears to maybe be some Hirst Arts planks for the floor.
The total price on this guy is probably up around $100 in parts, but man is it a slick model.