Germany: They've got an "H" license plate (historic — older than 30 years), are exempt from emissions laws and often you don't have to pay taxes on them.
There's usually exemption for historic cars (over 30 years old).
They shouldn't be. Aside the terrible emissions from the 2-stroke engine, they're pretty unsafe. I once had the misfortune to get a ride in W-Berlin in one (early nineties). The windows/interior are so oddly designed, you have a pretty poor view. That might not have been much of an issue in the DDR with the low traffic density then, but it's unfit for the current situation in most European cities or highways.