People turning up wearing street clothes and a pair of jandals/thongs/Havanas (or whatever you call beach slip on shoes). There's heaps of signs saying closed toe sports shoes only WITH pictures.

People (and so far it's only men) that sit down on the gym equipment and don't use it. Hey there's two couches to sit on in the corner. If you need a rest, sit over there. I shouldn't have to ask you to move so I can use the machine!