A cube Harb and I maintain for our playgroup.

This cube supports the following archetypes:

• Aggro;
  White, red and black boast quite an aggressive section of creatures making most combinations of colours consistently go 1,2,3 drop.

• Midrange;
  There is a slew of 3-5 mana value spells included in every colour making creature based value decks perform exactly like you expect them to.

• Control;
  Both white and black offer quite a lot of removal options from single target removal to boardwipes. Blue is very counterspell centric which makes azorius, dimir and esper control all viable.

• Combo;
  There is quite a few established and yet undiscovered (my playgroup keeps suprising me) combo archetypes that either win you the game outright or set up a winning boardstate. A few examples are: splintertwin, reanimator, channel. There are also a lot of highly synergistic subthemes that can win the game through outvalue-ing the opponent, a few examples are: aristocrats, flicker, artifacts matter, token strategies.