Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Runaway Steam-Kin

Whenever you cast a red spell, if this creature has fewer than three +1/+1 counters on it, put a +1/+1 counter on this creature.
Remove three +1/+1 counters from this creature: Add {R}{R}{R}.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Sol Ring

Curse of Opulence

Enchant player
Whenever enchanted player is attacked, create a Gold token. Each opponent attacking that player does the same. (A Gold token is an artifact with "Sacrifice this token: Add one mana of any color.")

Rograkh, Son of Rohgahh

First strike, menace, trample
Partner (You can have two commanders if both have partner.)

Spell Satchel

Magecraft — Whenever you cast or copy an instant or sorcery spell, put a book counter on this artifact.
{T}, Remove a book counter from this artifact: Add {C}.
{3}, {T}, Remove three book counters from this artifact: Draw a card.

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.)