Goblin Warchief

Goblin spells you cast cost {1} less to cast.
Goblins you control have haste.

Dogpile

Dogpile deals damage to any target equal to the number of attacking creatures you control.

Goblin Instigator

When Goblin Instigator enters, create a 1/1 red Goblin creature token.

Mountain

Hobgoblin Bandit Lord

Other Goblins you control get +1/+1.
{R}, {T}: Hobgoblin Bandit Lord deals damage equal to the number of Goblins that entered the battlefield under your control this turn to any target.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Ib Halfheart, Goblin Tactician

Whenever another Goblin you control becomes blocked, sacrifice it. If you do, it deals 4 damage to each creature blocking it.
Sacrifice two Mountains: Create two 1/1 red Goblin creature tokens.

Goblin Arsonist

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

Rundvelt Hordemaster

Other Goblins you control get +1/+1.
Whenever Rundvelt Hordemaster or another Goblin you control dies, exile the top card of your library. If it's a Goblin creature card, you may cast that card until the end of your next turn.

Enterprising Scallywag

At the beginning of your end step, if you descended this turn, create a Treasure token. (You descended if a permanent card was put into your graveyard from anywhere.)

Krenko, Tin Street Kingpin

Whenever Krenko, Tin Street Kingpin attacks, put a +1/+1 counter on it, then create a number of 1/1 red Goblin creature tokens equal to Krenko's power.

Crash Through

Creatures you control gain trample until end of turn. (Each of those creature can deal excess combat damage to the player or planeswalker it's attacking.)
Draw a card.

Bloodmark Mentor

Red creatures you control have first strike.

Krenko, Mob Boss

{T}: Create X 1/1 red Goblin creature tokens, where X is the number of Goblins you control.

Chain Reaction

Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.

Cleaver Riot

Creatures you control gain double strike until end of turn. (They deal both first-strike and regular combat damage.)