Zepto is about as small as you can get with pixel fonts without sub-pixel rendering. Featured on Make: A tiny screen font you can actually download and use, free. For optimal use, please turn font anti-aliasing off and set at a size of 8px with image resolution set to 72ppi.

The original Headhunter shareware font was created in ©1992 by the famous D. Rakowski. It consisted of 63 unique skeletal Glyphs, including Capital A-Z, and a few bone symbols, but lacked lowercase and numerals. He has since abandoned his fonts to pursue other things. (You can download it from FontSquirrel for free.) I've always enjoyed this limited Halloween font, but its incompleteness had to be rectified; thus I took it upon myself to delve slightly into the world of typography, resulting in the birth of HeadhunterTwo. I've slightly reworked his original contribution and "fleshed out" more of the font than necessary. As of this writing, it consists of 777+ Glyphs and passes Underware's compatibility test for Latin Plus (Supporting 219 Latin based languages, which are spoken in 212 countries.)