butt heads

bang some heads together

Attempt to get results from a previously ineffectual or argumentative group, typically by coercion or force.

bust one's butt

To work exceptionally hard.

butt in

To join a conversation or situation in which one is not welcome or invited; to interject (connotes a rude or discourteous interruption).

butt up

To touch closely, to scrape (against); to press firmly (against).

full butt

headfirst with full force

get one's butt somewhere

Go somewhere, especially quickly.

heads or tails

The practice of flipping a coin in the air, to choose between two alternatives based on which side lands face up.

heads will roll

Some people will be fired for incompetence.