Goblin Ringleader

Haste (This creature can attack and {T} as soon as it comes under your control.)
When Goblin Ringleader enters the battlefield, reveal the top four cards of your library. Put all Goblin cards revealed this way into your hand and the rest on the bottom of your library in any order.

Cavern of Souls

As Cavern of Souls enters the battlefield, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

Kiki-Jiki, Mirror Breaker

Haste
{T}: Create a token that's a copy of target nonlegendary creature you control, except it has haste. Sacrifice it at the beginning of the next end step.

Boggart Harbinger

When Boggart Harbinger enters the battlefield, you may search your library for a Goblin card, reveal it, then shuffle and put that card on top.

Sling-Gang Lieutenant

When Sling-Gang Lieutenant enters the battlefield, create two 1/1 red Goblin creature tokens.
Sacrifice a Goblin: Target player loses 1 life and you gain 1 life.

Mogg War Marshal

Echo {1}{R} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Mogg War Marshal enters the battlefield or dies, create a 1/1 red Goblin creature token.

Goblin Matron

When Goblin Matron enters the battlefield, you may search your library for a Goblin card, reveal that card, put it into your hand, then shuffle.