Schwartz is the place to go for smoked meat.
Also, if you like small craft breweries, then you need to check out Brewtopia on crescent St. Their beer is so tasty, their flavors are out of this world.
There is also "real bagel" where you can get awesome bagels that they make inside the shop. I prefer Montreal style bagels to New York style.
http://www.realbagel.com/
bagels = best souvenir ever.
Also, if you are from the states be sure to get some coffee crisps, all dressed/ketchup flavored chips and other delicious Canada-only snack foods.