Hell's CuboidThe concept of the Ghost Cube applied to a 3x3x4 with the offset layers along the 3-layered axis.
Holey X-BlockA Holey Skewb (aka Void Skewb) that has been extended on two sides.
Hollow 1x2x2Probably the most minimalistic twisty puzzle although by far not the most trivial to make.
i! cubeCombines the concept of the I-Cube with the Bump Cube.
King's CubeA cornerless 3x3x3 with additional pieces which gave it the look of a 3x3x5.
KolasA 3x3x3 bandaged and extended with cubies glued on.