It's simple, when in London you must eat a Salt Beef Sandwich and In Montreal you must eat a Smoked Meat Sandwich.
Ask anyone in the city and they will all point you to Schwartz's deli. While they are known for their smoked meat, their slapstick comedy should be an honorable mention. During my stay I was ribbed by the staff a few times (all in good fun of course) and saw they do the same to other patrons.
They were good at their job and I am sure that they get asked 1000 times a day on what to order especially since everything is in French. They suggested a medium smoked meat sandwich, fries, pickle and a black cherry soda.
I must say that I liked the smoked meat better than salt beef (sorry London). The best way to eat one of these is "medium" (with a bit of fat) and fresh cut. I did notice that towards the end of my meal the meat did dry out a bit; so I would hate to imagine what a 8hr old smoked mat sandwich would look and taste like.. eek...
Like any city icon it gets quite crowded with both locals and tourists so my advice would be to go during off peak hours. I arrived at 10pm an had no problem getting a seat at the counter. If you come at any other time be prepared to wait.. Remember that it is worth the wait! Don't waste your time getting a smoked meat sandwich from anywhere else but here.