Native3D is lightweight  3D engine from GameDevelop.
Built on FP10 API, but you can find Molehill version too.

Native3D (using Molehill/Stage3D):

[ Example 01 ]
[ Example 02 ]

Native3d (using only FP10 API):

[ Flat Shading ]
[ Sphere Panorama ]
[ 3D Maze ]
[ Shadows ]
[ TargetCamera ] 

Sources available at GoogleCode Repository.