Originally Posted by Shareholder

This is rather academic because no country would let a Canadian citizen or resident in without a valid passport (issued by Canada or another country) and that country's entry visa, so there's hardly any way a natural born or naturalized Canadian could return without such a passport...even though to get back in does not require one.

But to dive into the realm of academia, I suppose to be blunt you'd first be stereotyped based on your pattern of speech and ethnicity. If the immigration officer was satisfied you "looked and sounded" like a Canadian (and don't challenge me on what that means), then your provincial driver's license or health card would be enough as long as it had a photo on it, with perhaps something like a business card, employer ID or other form of corroborating item (like a credit card). If there was suspicion about one's "Canadianess" then the basic requirement that landed immigrants carry the always required "papers" and naturalized citizens their citizenship card should resolve that issue. Such documents are provided for just such purposes. This would apply for entry by car, boat or plane...or foot.