Tale of Katara and Toph

Creatures you control have "Whenever this creature becomes tapped for the first time during each of your turns, put a +1/+1 counter on it."

Saint Traft and Rem Karolus

Whenever Saint Traft and Rem Karolus becomes tapped, create a 1/1 red Human creature token if this is the first time this ability has resolved this turn. If it's the second time, create a 1/1 blue Spirit creature token with flying. If it's the third time, create a 4/4 white Angel creature token with flying.
Whenever you cast a spell that has convoke, untap Saint Traft and Rem Karolus.

Magda, Brazen Outlaw

Other Dwarves you control get +1/+0.
Whenever a Dwarf you control becomes tapped, create a Treasure token.
Sacrifice five Treasures: Search your library for an artifact or Dragon card, put that card onto the battlefield, then shuffle.

Kilo, Apogee Mind

Haste
Whenever Kilo becomes tapped, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Pain Seer

Inspired — Whenever this creature becomes untapped, reveal the top card of your library and put that card into your hand. You lose life equal to that card's mana value.

Hair-Strung Koto

Tap an untapped creature you control: Target player mills a card.

Neerdiv, Devious Diver

Whenever Neerdiv becomes tapped, target player mills cards equal to its power.
Whenever you cast a spell from your graveyard or activate an ability of a card in your graveyard, draw a card and put a +1/+1 counter on Neerdiv.

Vampire Envoy

Flying
Whenever this creature becomes tapped, you gain 1 life.

Nullmage Shepherd

Tap four untapped creatures you control: Destroy target artifact or enchantment.

Fallowsage

Whenever this creature becomes tapped, you may draw a card.

Judge of Currents

Whenever a Merfolk you control becomes tapped, you may gain 1 life.

Oreskos Sun Guide

Inspired — Whenever this creature becomes untapped, you gain 2 life.

Aurelia, the Warleader

Flying, vigilance, haste
Whenever Aurelia attacks for the first time each turn, untap all creatures you control. After this phase, there is an additional combat phase.

Moonfolk Puzzlemaker

Flying
Whenever this creature becomes tapped, scry 1.

Tui and La, Moon and Ocean

Whenever Tui and La become tapped, draw a card.
Whenever Tui and La become untapped, put a +1/+1 counter on them.

Glare of Subdual

Tap an untapped creature you control: Tap target artifact or creature.

Drumbellower

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

Intruder Alarm

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

Merieke Ri Berit

Merieke Ri Berit doesn't untap during your untap step.
{T}: Gain control of target creature for as long as you control Merieke Ri Berit. When Merieke Ri Berit leaves the battlefield or becomes untapped, destroy that creature. It can't be regenerated.

Cryptolith Rite

Creatures you control have "{T}: Add one mana of any color."

Stonybrook Schoolmaster

Whenever this creature becomes tapped, you may create a 1/1 blue Merfolk Wizard creature token.

Intrepid Hero

{T}: Destroy target creature with power 4 or greater.

Seedborn Muse

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

Kyren Negotiations

Tap an untapped creature you control: This enchantment deals 1 damage to target player or planeswalker.

Starfighter Pilot

Whenever this creature becomes tapped, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

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.)

Dazzling Theater // Prop Room

Goblin Medics

Whenever this creature becomes tapped, it deals 1 damage to any target.

Siren of the Silent Song

Flying
Inspired — Whenever this creature becomes untapped, each opponent discards a card, then each opponent mills a card.

Chrome Companion

Whenever this creature becomes tapped, you gain 1 life.
{2}, {T}: Put target card from a graveyard on the bottom of its owner's library.

Servant of Tymaret

Inspired — Whenever this creature becomes untapped, each opponent loses 1 life. You gain life equal to the life lost this way.
{2}{B}: Regenerate this creature.

Immersturm Predator

Flying
Whenever this creature becomes tapped, exile up to one target card from a graveyard and put a +1/+1 counter on this creature.
Sacrifice another creature: This creature gains indestructible until end of turn. Tap it.

Quest for Renewal

Whenever a creature you control becomes tapped, you may put a quest counter on this enchantment.
As long as there are four or more quest counters on this enchantment, untap all creatures you control during each other player's untap step.

Thermo-Alchemist

Defender
{T}: This creature deals 1 damage to each opponent.
Whenever you cast an instant or sorcery spell, untap this creature.

Aggravated Assault

{3}{R}{R}: Untap all creatures you control. After this main phase, there is an additional combat phase followed by an additional main phase. Activate only as a sorcery.

Unruly Catapult

Emmara, Soul of the Accord

Whenever Emmara becomes tapped, create a 1/1 white Soldier creature token with lifelink.

Earthcraft

Tap an untapped creature you control: Untap target basic land.

Anzrag, the Quake-Mole

Whenever Anzrag 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.

Attentive Sunscribe

Whenever this creature becomes tapped, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Kirol, Attentive First-Year

Tap two untapped creatures you control: Copy target triggered ability you control. You may choose new targets for the copy. Activate only once each turn.

Sphinx's Disciple

Flying
Inspired — Whenever this creature becomes untapped, draw a card.

Elven Chorus

You may look at the top card of your library any time.
You may cast creature spells from the top of your library.
Creatures you control have "{T}: Add one mana of any color."

Lobber Crew

Defender
{T}: This creature deals 1 damage to each opponent.
Whenever you cast a multicolored spell, untap this creature.

Opposition

Tap an untapped creature you control: Tap target artifact, creature, or land.

Samite Herbalist

Whenever this creature becomes tapped, you gain 1 life and scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Awakening

At the beginning of each upkeep, untap all creatures and lands.

Murkfiend Liege

Other green creatures you control get +1/+1.
Other blue creatures you control get +1/+1.
Untap all green and/or blue creatures you control during each other player's untap step.

Prosperous Partnership

When this enchantment enters, create two 1/1 green and white Citizen creature tokens.
Tap three untapped creatures you control: Create a Treasure token.

Veteran of the Depths

Whenever this creature becomes tapped, you may put a +1/+1 counter on it.

Nettle Drone

Devoid (This card has no color.)
{T}: This creature deals 1 damage to each opponent.
Whenever you cast a colorless spell, untap this creature.

Compassionate Healer

Whenever this creature becomes tapped, you gain 1 life and scry 1. (Look at the top card of your library. You may put it on the bottom.)

Wildfire Awakener

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
When this creature enters, create X 1/1 red Elemental creature tokens with "Whenever this token becomes tapped, it deals 1 damage to target player."

Enduring Vitality

Vigilance
Creatures you control have "{T}: Add one mana of any color."
When Enduring Vitality dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)

Spireside Infiltrator

Whenever this creature becomes tapped, it deals 1 damage to each opponent.

Wylie Duke, Atiin Hero

Vigilance
Whenever Wylie Duke becomes tapped, you gain 1 life and draw a card.

Night Market Lookout

Whenever this creature becomes tapped, each opponent loses 1 life and you gain 1 life.