Krark, the Thumbless

Whenever you cast an instant or sorcery spell, flip a coin. If you lose the flip, return that spell to its owner's hand. If you win the flip, copy that spell, and you may choose new targets for the copy.
Partner (You can have two commanders if both have partner.)

Grim Wanderer

Flash
Tragic Backstory — Cast this spell only if a creature died this turn.

Vial Smasher the Fierce

Whenever you cast your first spell each turn, choose an opponent at random. Vial Smasher the Fierce deals damage equal to that spell's mana value to that player or a planeswalker that player controls.
Partner (You can have two commanders if both have partner.)

Knucklebone Witch

Whenever a Goblin you control is put into a graveyard from the battlefield, you may put a +1/+1 counter on Knucklebone Witch.

Mad Auntie

Other Goblin creatures you control get +1/+1.
{T}: Regenerate another target Goblin.

Warren Soultrader

Pay 1 life, Sacrifice another creature: Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")