I have an F-1 visa in the US and I was planning on flying home after exams, but before going back home I want to spend some time in Canada where I have a valid ten-year multiple-entry visa. The cheapest flight available requires me to fly back into the US for a connecting flight. My status is still valid. Do I need to get a new transit/visitor's visa (in addition to my F-1 visa) in this situation, even if I am just passing through the airport for a few hours? Thanks for your attention!
If you're allowed to enter for visit or residency, you can also enter for transit. A visitor or residency visa is thus superior to a transit visa.
This goes for all countries in the world.