Famous Last Words & The Wars, both by Findley, also A Complicated Kindness by Toews would be among my favourites.
I guess my least favourites begin with everything else.
What’s Bred in the Bone by Robertson Davies, probably. I loved the Cornish Trilogy as a whole, though the final installment was a bit thin compared to the other two.
As for least favourite, that would have to be The Tent Peg by Aritha van Herk. Utter drivel. My (at the time) gf and I used to mock it mercilessly. I only read it because a friend of hers recommended it, and she found it so funny she forced me to read it too.
Just popping back in to say how much I enjoyed the comments from everyone. There’s some books here that I’ll have to read (or re-read).
Every so often the Folio Society asks its members what books they would like to see published by Folio; I keep plugging Davies and Mitchell, but so far to no effect. 
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They’re not really novels, but I rather liked Farley Mowat’s early work; in particular The Dog Who Wouldn’t Be and The Boat who Wouldn’t Float.
Stephen Leacock remains a favourite, especially his Sunshine Sketches of a Little Town.
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We appear to have been reading exactly the same stuff in our youth. 
It helped that the Dog Who Wouldn’t Be is set in Saskatchewan, and begins with a description of the Mowat family re-entering Canada at Estevan, during the Depression, ravaged by strip-mining - that was the first piece of literature that actually mentioned an area that I had personal familiarity with, which really helped to connect.
(Similarly, British authors like Wodehouse and Mortimer occasionally mention Saskatoon, Saskatchewan, but I think it’s just because they think it sounds funny. But I like the shout-out nonetheless.)
An all-time favorite – didn’t know he was Canadian.
Haven’t read that one but really enjoyed Irma Voth.
Loved that one too (the title in the US was Nobody Knows My Name – another author I didn’t realize was Canadian.
we’re anonymous, that way - we can pass for Americans as needed.
(when the invasion from the North starts, you’re in trouble – but I’ve said too much…)
A little surprised there’s so little love here for Carol Shields–LARRY’S PARTY in particular, but the STONE DIARIES was also excellent.
Another vote for Davies; my faves are Fifth Business and Rebel Angels.
I hunted down first Canadian editions of his three trilogies and a few of his other works. Great reading on a number of levels. Why he didn’t get the Nobel during his lifetime is beyond me…
Tigana, by Guy Gavriel Kay. Obviously.