Back in 1968 in Iran an AB206A on pop-out flotation gear, (High skids etc), landed on the metal heli-deck of a rig and all pax got out and disappeared down the stairs, leaving the pilot with a heavy HF radio, (or similar), in the baggage bay and the helicopter out of balance. The rule was, 'never shut down on a helideck if there is only room for one', the logic being that if you couldn't get a start you were stuck until sea born help arrived.
The captain frictioned down and went round to get the piece of equipment out but the 206 started to move, (metal skids over a metal deck), and the helicopter eventually went over the side. Luckily it went into the sea and no one was injured.