Snappy title eh? And in no way misleading! Huzzah!
For me.... Night Goblins. There's just something about the little bundles of black clad viciousness that appeals.
Models wise, they're awesome. All Goblins are. Suitably small and weedy, and still manage to look pretty pathetic, even when fielded in a massive block.
Units? Love them to bits! Big block may look weedy, but looks impressive. Squigs are all shades of awesome (but mostly red and ivory). Squig Hoppers, Mangler Squigs, Squig Gobbas, Trolls.... There is nothing I don't like about the diminutive psychopaths.
Background? A total and utter disregard for life. Even their own. I love the ambiguity as to whether or not they just don't care, or are too dim to grasp the concept!
But....but.....all that painting. Stuff the cost. If I wants it, I'll buys it! But the sheer number of models? And the conversion/dioramas practically demanded.....ARRGH!