One manoeuvre I used to enjoy was a max power climb from the normal hover, increasing negative airspeed to around -ve 25 kts and retracting the landing gear. At 450-500 feet agl, the cyclic was moved sharply forwards, and the collective lowered to about half the previous setting.
The aircraft nosed very sharply over to 90 degrees nose down, by about 400 ft agl. Once fully vertical, full right cyclic (to the mechanical stop) and some right yaw pedal rolled the aircraft 180 degrees whilst maintaing the 90 degrees nose down descent. It was then just a matter of a natural easing out of the dive, on the reciprocal heading, to level flight at about 50 agl and 120 kts.
Unfortunately it was latter banned as another display pilot (well two others actually, on separate occasions) managed to get the tail rotor blades to hit the inclined tail structure, even though when the blade hinges hit their stops there should have been about 12 inches of clearance from blade tip to hull!