Other stuff on an LS which can cause problems is any loose objects. This can be stuff as small as sand/dust/snow which recirculate in the downwash and impede visibility - "brownout/whiteout". Or it can be rubbish - plastic bags, corrugated iron, cardboard. Anything lying around that catches enough downwash can suddenly fly up out of nowhere and go through the main or tail rotor disc. Even a plastic carrier bag going through the tail rotor can cause serious damage, because of the speed it s turning at.
As Jack says, you then have the human element of the problem. You never know when our wonderful public might throw a brick or a bottle into the rotors to see what will happen, or they will push a stick through the fenestron/air intakes if you are not watching whilst the aircraft is shut down. At night time, they will shine laser pointers or powerful torches at you to see what will happen, or they will take a flash photo, and blind your night vision as you land/take off.
Animals can be a problem - you dont want a spooked horse or herd of cows stampeding towards your (very thin) aluminium and plastic pilots door!
Its on the ground or close to it that all this unexpected stuff can happen, so you have to be ready for anything!