Puppet Strings

{2}, {T}: You may tap or untap target creature.

Bounding Krasis

Flash (You may cast this spell any time you could cast an instant.)
When Bounding Krasis enters, you may tap or untap target creature.

Wirewood Symbiote

Return an Elf you control to its owner's hand: Untap target creature. Activate only once each turn.

Kiora, Behemoth Beckoner

Whenever a creature you control with power 4 or greater enters, draw a card.
−1: Untap target permanent.

Patriar's Seal

{T}: Add one mana of any color.
{1}, {T}: Untap target legendary creature you control.

Chain Stasis

You may tap or untap target creature. Then that creature's controller may pay {2}{U}. If the player does, they may copy this spell and may choose a new target for that copy.

Aim High

Untap target creature. It gets +2/+2 and gains reach until end of turn. (It can block creatures with flying.)

Twiddle

You may tap or untap target artifact, creature, or land.

Hyrax Tower Scout

When Hyrax Tower Scout enters, untap target creature.

Jolt

You may tap or untap target artifact, creature, or land.
Draw a card at the beginning of the next turn's upkeep.

Retreat to Coralhelm

Landfall — Whenever a land you control enters, choose one —
• You may tap or untap target creature.
• Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Stonybrook Angler

{1}{U}, {T}: You may tap or untap target creature.

Twitch

You may tap or untap target artifact, creature, or land.
Draw a card.

Initiate's Companion

Whenever Initiate's Companion deals combat damage to a player, untap target creature or land.

Corridor Monitor

When Corridor Monitor enters, untap target artifact or creature you control.

Puppeteer

{U}, {T}: You may tap or untap target creature.

Quirion Ranger

Return a Forest you control to its owner's hand: Untap target creature. Activate only once each turn.

Mirran Spy

Flying
Whenever you cast an artifact spell, you may untap target creature.

Spidery Grasp

Untap target creature. It gets +2/+4 and gains reach until end of turn. (It can block creatures with flying.)

Niblis of the Breath

Flying
{U}, {T}: You may tap or untap target creature.

Ornamental Courage

Untap target creature. It gets +1/+3 until end of turn.

Ghostly Touch

Enchant creature
Enchanted creature has "Whenever this creature attacks, you may tap or untap target permanent."

Gift of Growth

Kicker {2} (You may pay an additional {2} as you cast this spell.)
Untap target creature. It gets +2/+2 until end of turn. If this spell was kicked, that creature gets +4/+4 until end of turn instead.

Curse of Inertia

Enchant player
Whenever a player attacks enchanted player with one or more creatures, that attacking player may tap or untap target permanent of their choice.

Scryb Ranger

Flash
Flying, protection from blue
Return a Forest you control to its owner's hand: Untap target creature. Activate only once each turn.

Civic Gardener

Whenever Civic Gardener attacks, untap target creature or land.

Thassa's Ire

{3}{U}: You may tap or untap target creature.

Refocus

Fyndhorn Brownie

Prime Speaker Vannifar

{T}, Sacrifice another creature: Search your library for a creature card with mana value equal to 1 plus the sacrificed creature's mana value, put that card onto the battlefield, then shuffle. Activate only as a sorcery.

Infuse

Untap target artifact, creature, or land.
Draw a card at the beginning of the next turn's upkeep.

Seeker of Skybreak

Emerald Charm

Choose one —
• Untap target permanent.
• Destroy target non-Aura enchantment.
• Target creature loses flying until end of turn.