I know the case (a long time ago) where the corroded trap-door of an old helideck hatch, collapsed under the pressure of an Alouette 3 main gear wheel. The helicopter capsized an was written off.
I also remember a "welcome aboard" aluminium panel sign, flying off in a landing SA 330 damaging its tail rotor blades....
And many other various incidents alike (i.e empty drums rolling overboard in rotor downwash, torn windsock....)