Just as each Cube exists, there are special limited edition versions of them as well, except for the Mods and Series 1.
Here are pictures of all the cubes limited edition variants:
Series 2-Mic & Hans
Dusty & Handy
Toner & Dash (These are the most common variants of Special Edition cubes, along with Chief & Sparky)
Chief & Sparky
Slugger & Kicks (These are the rarest limited edition variants of any cube)
Grinder & Slam