Cacophony Scamp

Whenever Cacophony Scamp deals combat damage to a player, you may sacrifice it. If you do, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
When Cacophony Scamp dies, it deals damage equal to its power to any target.

Raging Goblin

Haste (This creature can attack and {T} as soon as it comes under your control.)

Goblin Brigand

Goblin Brigand attacks each combat if able.

Rouse the Mob

Strive — This spell costs {2}{R} more to cast for each target beyond the first.
Any number of target creatures each get +2/+0 and gain trample until end of turn.

Mudbrawler Cohort

Haste
Mudbrawler Cohort gets +1/+1 as long as you control another red creature.

Exuberant Fuseling

Trample
Exuberant Fuseling gets +1/+0 for each oil counter on it.
When Exuberant Fuseling enters and whenever another creature or artifact you control is put into a graveyard from the battlefield, put an oil counter on Exuberant Fuseling.

Goblin Fireslinger

{T}: Goblin Fireslinger deals 1 damage to target player or planeswalker.

Goblin Heelcutter

Whenever Goblin Heelcutter attacks, target creature can't block this turn.
Dash {2}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Goblin Banneret

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
{1}{R}: Goblin Banneret gets +2/+0 until end of turn.

Warlord's Fury

Creatures you control gain first strike until end of turn.
Draw a card.

Goblin Arsonist

When Goblin Arsonist dies, you may have it deal 1 damage to any target.

Hobgoblin Captain

Pack tactics — Whenever Hobgoblin Captain attacks, if you attacked with creatures with total power 6 or greater this combat, Hobgoblin Captain gains first strike until end of turn.

Mardu Scout

Dash {1}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Goblin Tunneler

{T}: Target creature with power 2 or less can't be blocked this turn.

Goblin Javelineer

Haste
Whenever Goblin Javelineer becomes blocked, it deals 1 damage to target creature blocking it.

Goblin Freerunner

Surge {1}{R} (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.)
Menace (This creature can't be blocked except by two or more creatures.)

Krenko's Command

Create two 1/1 red Goblin creature tokens.

Swarming Goblins

When Swarming Goblins enters, roll a d20.
1—9 | Create a 1/1 red Goblin creature token.
10—19 | Create two of those tokens.
20 | Create three of those tokens.

Comet Storm

Multikicker {1} (You may pay an additional {1} any number of times as you cast this spell.)
Choose any target, then choose another target for each time this spell was kicked. Comet Storm deals X damage to each of them.

Mountain

Battle Cry Goblin

{1}{R}: Goblins you control get +1/+0 and gain haste until end of turn.
Whenever Battle Cry Goblin attacks, if you attacked with creatures with total power 6 or greater this combat, create a 1/1 red Goblin creature token that's tapped and attacking.