Harried Dronesmith and Breath of Fury on the battlefield.
An opponent cannot block creatures you control.
Breath of Fury attached to any other creature you control that does not have summoning sickness.
At the beginning of your combat phase, Harried Dronesmith triggers, creating a 1/1 Thopter artifact creature token with flying and haste.
Deal combat damage to an opponent 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 Thopter, then causing you to untap all creatures you control and to get an additional combat phase after this one.