The Floppy Cube is a Rubik's Cube variant with a flat shape (1x3x3). It's like a single layer of a normal Rubik's Cube taken out, with stickers applied to all sides. Solving the Floppy Cube is extremely easy, and it makes a good "first cube" for aspiring cubists.
It has never been released under the official Rubik's brand, but is still mass-produced and therefore counts as a product of its own.
The Floppy cube was invented by Katsuhiko Okamoto. It is a cube that is only capable of doing 180 degree turns.
There is another version called the 'super floppy', that can shapeshift. You can turn one face 90 degrees, and then you can turn another face (2 cubies) 90 or 180 degrees.