Directors of Canadian companies who are living abroad is probably one example.
Also, people who, say, commute from CA to the US on a daily basis will generally be exempt from Canadian taxes because the work is performed in the US (just an example, I have no idea whether you can commute from CA -> US on a daily basis)
Well, I was "taxed" on my Chinese income, but never paid a dime. Foreign tax credits and foreign income exclusions mean most of us pay nothing (well, we pay Chinese taxes, just not US taxes).
Also, people who, say, commute from CA to the US on a daily basis will generally be exempt from Canadian taxes because the work is performed in the US (just an example, I have no idea whether you can commute from CA -> US on a daily basis)