Brash Taunter

Indestructible
Whenever this creature is dealt damage, it deals that much damage to target opponent.
{2}{R}, {T}: This creature fights another target creature.

Hungering Hydra

This creature enters with X +1/+1 counters on it.
This creature can't be blocked by more than one creature.
Whenever this creature is dealt damage, put that many +1/+1 counters on it. (It must survive the damage to get the counters.)

Fiendlash

Equipped creature gets +2/+0 and has reach.
Whenever equipped creature is dealt damage, it deals damage equal to its power to target player or planeswalker.
Equip {2}{R}

Selvala, Heart of the Wilds

Whenever another creature enters, its controller may draw a card if its power is greater than each other creature's power.
{G}, {T}: Add X mana in any combination of colors, where X is the greatest power among creatures you control.

Search for Tomorrow

Search your library for a basic land card, put it onto the battlefield, then shuffle.
Suspend 2—{G} (Rather than cast this card from your hand, you may pay {G} and exile it with two time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)

Cacophodon

Enrage — Whenever this creature is dealt damage, untap target permanent.

Donna Noble

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.)
Whenever Donna Noble or a creature it's paired with is dealt damage, Donna Noble deals that much damage to target opponent.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Utopia Sprawl

Enchant Forest
As this Aura enters, choose a color.
Whenever enchanted Forest is tapped for mana, its controller adds an additional one mana of the chosen color.

Sporeweb Weaver

Reach, hexproof from blue
Whenever Sporeweb Weaver is dealt damage, you gain 1 life and create a 1/1 green Saproling creature token.

Needletooth Raptor

Enrage — Whenever this creature is dealt damage, it deals 5 damage to target creature an opponent controls.

Coalhauler Swine

Whenever this creature is dealt damage, it deals that much damage to each player.

Ripjaw Raptor

Enrage — Whenever this creature is dealt damage, draw a card.

Broodhatch Nantuko

Whenever this creature is dealt damage, you may create that many 1/1 green Insect creature tokens.
Morph {2}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Frilled Deathspitter

Enrage — Whenever this creature is dealt damage, it deals 2 damage to target opponent or planeswalker.

Screaming Nemesis

Haste
Whenever this creature is dealt damage, it deals that much damage to any other target. If a player is dealt damage this way, they can't gain life for the rest of the game.

Boros Reckoner

Whenever this creature is dealt damage, it deals that much damage to any target.
{R/W}: This creature gains first strike until end of turn.

Urban Daggertooth

Vigilance
Enrage — Whenever this creature is dealt damage, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Ranging Raptors

Enrage — Whenever this creature is dealt damage, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Raptor Hatchling

Enrage — Whenever this creature is dealt damage, create a 3/3 green Dinosaur creature token with trample.

Mogg Maniac

Whenever this creature is dealt damage, it deals that much damage to target opponent or planeswalker.

Polyraptor

Enrage — Whenever this creature is dealt damage, create a token that's a copy of this creature.

Pyrohemia

At the beginning of the end step, if no creatures are on the battlefield, sacrifice this enchantment.
{R}: This enchantment deals 1 damage to each creature and each player.

Overgrown Armasaur

Enrage — Whenever this creature is dealt damage, create a 1/1 green Saproling creature token.

Saber Ants

Whenever this creature is dealt damage, you may create that many 1/1 green Insect creature tokens.

Flumph

Defender, flying
Whenever this creature is dealt damage, you and target opponent each draw a card.

Blazing Sunsteel

Equipped creature gets +1/+0 for each opponent you have.
Whenever equipped creature is dealt damage, it deals that much damage to any target.
Equip {4}

Stuffy Doll

Indestructible
As this creature enters, choose a player.
Whenever this creature is dealt damage, it deals that much damage to the chosen player.
{T}: This creature deals 1 damage to itself.

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Bellowing Aegisaur

Enrage — Whenever this creature is dealt damage, put a +1/+1 counter on each other creature you control.

Wayta, Trainer Prodigy

Haste
{2}{G}, {T}: Target creature you control fights another target creature. This ability costs {2} less to activate if it targets two creatures you control.
If a creature you control being dealt damage causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Druid's Call

Enchant creature
Whenever enchanted creature is dealt damage, its controller creates that many 1/1 green Squirrel creature tokens.

Wrathful Raptors

Trample
Whenever a Dinosaur you control is dealt damage, it deals that much damage to any target that isn't a Dinosaur.

Silverclad Ferocidons

Enrage — Whenever this creature is dealt damage, each opponent sacrifices a permanent of their choice.

Zalto, Fire Giant Duke

Trample
Whenever Zalto is dealt damage, venture into the dungeon. (Enter the first room or advance to the next room.)

Rite of Passage

Whenever a creature you control is dealt damage, put a +1/+1 counter on it. (It must survive the damage to get the counter.)

Trapjaw Tyrant

Enrage — Whenever this creature is dealt damage, exile target creature an opponent controls until this creature leaves the battlefield.

Hornet Nest

Defender (This creature can't attack.)
Whenever this creature is dealt damage, create that many 1/1 green Insect creature tokens with flying and deathtouch. (Any amount of damage a creature with deathtouch deals to a creature is enough to destroy it.)

Wild Growth

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional {G}.

Howlpack Avenger

Whenever a permanent you control is dealt damage, this creature deals that much damage to any target.
{1}{R}: This creature gets +2/+0 until end of turn.
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Ill-Tempered Loner

Whenever this creature is dealt damage, it deals that much damage to any target.
{1}{R}: This creature gets +2/+0 until end of turn.
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Ill-Tempered Loner // Howlpack Avenger

Strong, the Brutish Thespian

Ward {2}
Enrage — Whenever Strong is dealt damage, you get three rad counters and put three +1/+1 counters on Strong.
You gain life rather than lose life from radiation.

Siegehorn Ceratops

Enrage — Whenever this creature is dealt damage, put two +1/+1 counters on it. (It must survive the damage to get the counters.)

Feldon, Ronom Excavator

Haste
Feldon can't block.
Whenever Feldon is dealt damage, exile that many cards from the top of your library. Choose one of them. Until the end of your next turn, you may play that card.

Sun-Crowned Hunters

Enrage — Whenever this creature is dealt damage, it deals 3 damage to target opponent or planeswalker.

Expedited Inheritance

Whenever a creature is dealt damage, its controller may exile that many cards from the top of their library. They may play those cards until the end of their next turn.