Feeding stray cats.
I have own cat, but feeding him is a duty, and feeding a stray cats - a voluntary action with positive outcome for both sides: they are fed, and I have possibility to watch the different kinds of cats. Cat watching, as opposed to a popular bird watching?
When I visited another country with different laws about animal control, there was abandoned building with small park where the very large colony of stray cats lived. People came there regularly to feed them, some even give them a medical treatment. Not everyone has possibility to keep a cat.
I am currently collecting the little plastic tubes they make you blow into for random breath tests. I have about 20 so far. It is a hard one to collect as you can never tell when a booze bus is going to pop up, but eventually I'll have enough to build into small water fountain......oh that's my other hobby I make small table top water fountains........
collecting little plastic tubes: rare enough to say non-existant
tabletop fountains: pretty rare but we are definetly out here =)