"Fathammer Ltd.: Mobile 3D and Game Technologies. Fathammer is the leading provider of advanced 3D graphics and game technologies for mobile devices." (from the company website at http://www.fathammer.com/)
Fathammer is a Finnish company that develops game technology for portable platforms. It was founded in 2000. The founder, Samuli Syvähuoko, used to be in Remedy Entertainment and MadOnion.com. RJ Mical, the Chief Architect, used to do small and modest things like inventing Atari Lynx and AmigaOS Intuition UI. Likewise, many of the employees have background in game industry and especially in the demoscene (which is, of course, an excellent springboard to 3D game development world...)
At the moment, their primary product, with 1.0 released finally in 2002, is X-Forge, a 3D game engine that runs on Symbian platforms, WinCE (Smartphone and PocketPC), and Mobile Linux, also coming for PalmOS and a custom version is available for Game Boy Advance. From what I've seen (which isn't much), the game engine is pretty impressive; Slashdotters whined of crappy graphics but the stuff was pretty darn cool for a little iPaq with a little heart. =)