Joker CubeA 3x3x3 encapsulated with a 2x2x2 which pieces have cutouts showing the four suits of a french playing card deck.
Joseph ToysAnother cube of unknown origin. The choice of colours (body and stickers) is highly unusual.
Jumbo Magic CubeThis is huge (penny to show relative size). It is larger than a 4x4x4 or 5x5x5.
KakuroA 3x3x3 stickered with a japanese number riddle.
Ken KenA 3x3x3 stickered with a japanese number riddle.
Key 3x3x3A mass produced 3x3x3 reduced to a compact size and with a customly attached keyring.
Knitted CubeA very innovative "sticker" variation of the 3x3x3.
Kubche RubcheA version of the 3x3x3 from the 1980s produced in bulgaria