i only ever tip taxi drivers here in aus, because they typically make little money working long hours and often get treated like shit by people who suck.
edit: i should add that there is no industry or service i use here for which tipping is standard or even expected. maybe in higher-class restaurants/hotels, i don't know, but i cant see myself ever getting in the door of those joints. anyone who works in gaming (ie croupiers etc) it is illegal to tip