Victory Chimes

Untap this artifact during each other player's untap step.
{T}: A player of your choice adds {C}.

Seedborn Muse

Untap all permanents you control during each other player's untap step.

Bender's Waterskin

Untap this artifact during each other player's untap step.
{T}: Add one mana of any color.

Urban Burgeoning

Enchant land
Enchanted land has "Untap this land during each other player's untap step."

Prop Room

Untap each creature you control during each other player's untap step.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Dazzling Theater

Creature spells you cast have convoke. (Your creatures can help cast those spells. Each creature you tap while casting a creature spell pays for {1} or one mana of that creature's color.)
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)