Mini Ghost cubeThis is a hand made ghost cube, no new challenges, but is pink, tiny, handmade and awesome.
Mini MascotAnother mini 3x3x3, presumably from the original cube craze.
Mixup 3x3x3A 3x3x3 that allows swapping of centers with edges.
Mogwai CubeA 3x3x3 with fur and other materials instead of stickers.
Monoblock bandaged Cubes without cornersThis is a set of four bandaged cubes all bandaged by a single block. None of these blocks include a corner piece so they are not equivalent to a Siamese Cube of any kind.
Multi Gear Cube KitA generalized version of the Paso Doble. It allows all kinds of gearing ratios between opposite sides for all three axis.