This is where it started: Starter Cube. I've been adding cards from my personal collection and picking up new pieces to power the cube up.

This is a two-color cube with good enough fixing for splashing a third color. The archetypes are as follows:

WU -- Control. This archetype wants to remove creatures and counter spells before landing a big finisher.
UB -- Self mill/Reanimation. Mill your deck and reanimate big threats around turn 4 or 5.
BR -- Sacrifice creatures/recursion. Sacrifice ETB value creatures for value.
RG -- 4 power matters/Stompy. Ramp out big creatures fast, smash face.
GW -- Tokens, go wide. Make creature tokens, play anthems.
WB -- Sacrifice tokens. Make creature tokens, sacrifice for value.
UR -- Spellslinger/Instants and Sorceries matter. Cast cheap threats, defend them, remove opponent's creatures. Tempo spellslinger.
BG -- Self-mill value. Mill your deck and play threats that depend on your graveyard.
RW -- Go wide aggro. Make tokens, play cheap creatures and burn spells, kill your opponent fast.
GU -- +1/+1 counters/proliferate/copy. Put counters on creatures, copy your opponent's threats.

As a general rule, gold cards represent their archetype. If you're wheeling gold cards, it's likely other players aren't in those colors.

Other noteworthy includes:
Ral's Vanguard -- If you want to try this deckbuilding restriction, go ahead. Instants and sorceries only! You'll need to find a way to win...
4- or 5-color Goodstuff -- This is lightly supported, mostly because the mana fixing is great. Omnath goes well here. Jam as many gold cards as you can and hope you don't get beat down by aggro.