Once thing I've always wondered, do you tip taxi drivers? Most of them seem to run thier own vehicle, and flex price the fares, so seem to be working for themselves. Of course if you have a lot of luggage or other items they need to assist loading/unloading, a tip would be given, but what about a simple ride across town? You hop in, you hop out??
Always gets me wondering. I generally do tip at these times, following my usual, "When in doubt, tip". I'd rather be thought of as rude for being ignorant of custom, than rude for being cheap.