So you are too bored with small magic cubes? You should give the MoYu 21x21x21 Magic Cube a look. It is a giant stickerless cube with smooth turning. This cube has 2709 pieces and weighs in at 3.15kg. It measures 150 ×150 ×150 mm.
The bad news? Something like this doesn’t come cheap. More info is available here.