Anzrag, the Quake-Mole

Whenever Anzrag, the Quake-Mole becomes blocked, untap each creature you control. After this phase, there is an additional combat phase.
{3}{R}{R}{G}{G}: Anzrag must be blocked each combat this turn if able.

Ghalta, Primal Hunger

This spell costs {X} less to cast, where X is the total power of creatures you control.
Trample

Goblin Anarchomancer

Each spell you cast that's red or green costs {1} less to cast.

Sol Ring

Tyvar's Stand

Target creature you control gets +X/+X and gains hexproof and indestructible until end of turn. (A creature with hexproof and indestructible can't be the target of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy it.)

Garruk's Uprising

When Garruk's Uprising enters the battlefield, if you control a creature with power 4 or greater, draw a card.
Creatures you control have trample. (They can deal excess combat damage to the player or planeswalker they're attacking.)
Whenever a creature with power 4 or greater enters the battlefield under your control, draw a card.

Talisman of Impulse

{T}: Add {C}.
{T}: Add {R} or {G}. Talisman of Impulse deals 1 damage to you.

Arcane Signet

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

Indomitable Might

Flash
Enchant creature
Enchanted creature gets +3/+3.
Enchanted creature's controller may have it assign its combat damage as though it weren't blocked.

Gruul Signet

Obscuring Haze

If you control a commander, you may cast this spell without paying its mana cost.
Prevent all damage that would be dealt this turn by creatures your opponents control.

Mage Slayer

Whenever equipped creature attacks, it deals damage equal to its power to the player or planeswalker it's attacking.
Equip {3}

Declare Dominance

Target creature gets +3/+3 until end of turn. All creatures able to block it this turn do so.