My cube, which I've been working at for years, always updating and changing shape. It's based around the concept of "synergy" with inspiration from the limited format of Kaladesh. I wanted a cube where almost any combination of cards could create a fun deck, and I also wanted to support three or more colours in decks to further encourage playing around with the possibilities.

Example Two-Colour Archetypes:
WU: "Enters the Battlefield" effects
UB: Control
BR: Vampires
RG: Aggro
GW: Tokens (especially Phyrexian Golems)
WB: Lifegain
BG: +1/+1 Counters
GU: Ramp
UR: Spells Matter
RW: Artifact Creatures

Additionally, +1/+1 counters and tokens are two overarching themes throughout all colours.