Masonzero's Pauper Cube
A pauper cube with fairly broad themes, but with some effort you might find a particular synergy. While the below themes do exist, there is a lot of overlap, and you can create these themes and synergies across multiple colors.
Because commons generally are best at low mana value, the average mana cost of cards is fairly low, and there are generally very few over 4 mana, as most pauper-legal cards at that mana value are not playable unless they have some sort of cost reduction.
White-Blue: Fliers, Blink
Blue-Black: Control
Black-Red: Sacrifice aggro
Red-Green: Stompy, Lands in the graveyard
Green-White: Go wide
White-Black: Reanimate, Sacrifice
Blue-Red: Spells, Cycling
Black-Green: Graveyard
Red-White: Heroic aggro, Tokens
Green-Blue: Grindy value, +1/+1 counters