Metal Head is a 3D shooter with mechs developed and published by Sega and released for the Sega 32X add-on for the Sega Mega Drive in 1994. Rod_Wod found some screens from an early beta / prototype of Metal Head, in which the main robot was still an unfinished ensemble of basic polygons. Check the video below (from the final version) for comparison!
Thanks to Jason for the english corrections!
Video (Final Version):