The desert versions of the 7 and 10 (not sure if they made a 9 like that) as well, the Hog Hunter version of the BK9 (sharpened swedge from factory) and while I am not sure if it counts, the necker prototypes.
There are some roll stamped BK16's that are hollow ground in different thicknesses, as well as the first roll stamped ones in varying thicknesses, the Tweener protos (and there are more than the three that show up in the pics, at one point there were about 6-8 of them in all different styles and sizes).
And then as far as rarity goes, there is the ever elusive BK8, of which I think Bladite is the only person here that owns one, including Ethan.
EDIT: Yes, they made a desert version of the BK9.
Carbon San Mai BK11's, as well as it appears personally engraved BK13's from Shot Show 2009.
Also the various serrated versions that exist.