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.

Forest

Krenko, Mob Boss

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

Munitions Expert

Flash
When Munitions Expert enters, you may have it deal damage to target creature or planeswalker equal to the number of Goblins you control.

Mountain

Goblin Trashmaster

Other Goblins you control get +1/+1.
Sacrifice a Goblin: Destroy target artifact.

Zhur-Taa Goblin

Riot (This creature enters with your choice of a +1/+1 counter or haste.)

Goblin King

Other Goblins get +1/+1 and have mountainwalk.

Bloodmark Mentor

Red creatures you control have first strike.

Dropkick Bomber

Other Goblins you control get +1/+1.
{R}: Until end of turn, another target Goblin you control gains flying and "When this creature deals combat damage, sacrifice it."

Conspicuous Snoop

Play with the top card of your library revealed.
You may cast Goblin spells from the top of your library.
As long as the top card of your library is a Goblin card, Conspicuous Snoop has all activated abilities of that card.

Skirk Prospector

Goblin Chieftain

Haste (This creature can attack and {T} as soon as it comes under your control.)
Other Goblin creatures you control get +1/+1 and have haste.

Boartusk Liege

Trample
Other red creatures you control get +1/+1.
Other green creatures you control get +1/+1.

Grumgully, the Generous

Each other non-Human creature you control enters with an additional +1/+1 counter on it.