Aura of Dominion

Enchant creature
{1}, Tap an untapped creature you control: Untap enchanted creature.

Pestermite

Flash
Flying
When this creature enters, you may tap or untap target permanent.

Kiora, Behemoth Beckoner

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

Stonybrook Angler

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

Double Major

Copy target creature spell you control, except it isn't legendary if the spell is legendary. (A copy of a creature spell becomes a token.)

Clever Conjurer

Mage Hand — {T}: Untap target permanent not named Clever Conjurer. Activate only as a sorcery.

Bounding Krasis

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

Xavier Sal, Infested Captain

{T}, Remove a counter from another permanent you control: Populate. Activate only as a sorcery. (Create a token that's a copy of a creature token you control.)
{T}, Sacrifice another creature: Proliferate. Activate only as a sorcery. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Breaching Hippocamp

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, untap another target creature you control.

Hyrax Tower Scout

When this creature enters, untap target creature.

Kiora's Follower

Myojin of Cryptic Dreams

Myojin of Cryptic Dreams enters with an indestructible counter on it if you cast it from your hand.
Remove an indestructible counter from Myojin of Cryptic Dreams: Copy target permanent spell you control three times. (The copies become tokens.)

Intruder Alarm

Creatures don't untap during their controllers' untap steps.
Whenever a creature enters, untap all creatures.

Janjeet Sentry

When this creature enters, you get {E}{E} (two energy counters).
{T}, Pay {E}{E}: You may tap or untap target artifact or creature.

Ioreth of the Healing House

{T}: Untap another target permanent.
{T}: Untap two other target legendary creatures.

Lithoform Engine

{2}, {T}: Copy target activated or triggered ability you control. You may choose new targets for the copy.
{3}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy.
{4}, {T}: Copy target permanent spell you control. (The copy becomes a token.)

Minamo, School at Water's Edge

{T}: Add {U}.
{U}, {T}: Untap target legendary permanent.

Captain of the Mists

Whenever another Human you control enters, untap this creature.
{1}{U}, {T}: You may tap or untap target permanent.

Aphetto Alchemist

{T}: Untap target artifact or creature.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Kelpie Guide

{T}: Untap another target permanent you control.
{T}: Tap target permanent. Activate only if you control eight or more lands.

Vizier of Tumbling Sands

{T}: Untap another target permanent.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When you cycle this card, untap target permanent.

Thassa's Ire

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

Galvanic Alchemist

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as this creature is paired with another creature, each of those creatures has "{2}{U}: Untap this creature."

Second Wind

Enchant creature
{T}: Tap enchanted creature.
{T}: Untap enchanted creature.

Freed from the Real

Enchant creature
{U}: Tap enchanted creature.
{U}: Untap enchanted creature.

Deceiver Exarch

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, choose one —
• Untap target permanent you control.
• Tap target permanent an opponent controls.

Seeker of Skybreak

Forensic Researcher

{T}: Untap another target permanent you control.
{T}, Collect evidence 3: Tap target creature you don't control. (To collect evidence 3, exile cards with total mana value 3 or greater from your graveyard.)