General Kreat and Breath of Fury on the battlefield.
You control at least one Mountain.
You control at least one Goblin.
An opponent cannot block creatures you control.
Steps
Declare the creature with Breath of Fury attached, and at least one Goblin if the creature with Breath of Fury attached isn't an Assassin, as attackers.
General Kreat's first ability triggers, creating a 1/1 Goblin creature token that's tapped and attacking.
When the Goblin enters the battlefield, General Kreat's second ability triggers, dealing 1 damage to each opponent.
Deal combat damage using the creature that has Breath of Fury attached.
Breath of Fury triggers, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to the Goblin token, then causing you to untap all creatures you control and to get an additional combat phase after this one.