If you're in Montreal, you have to stop by here for a poutine. Not just any poutine, you have literally dozens of choices for whatever suits your taste. There are Mexican, Meat lovers, Veggie, Classic and the list goes on. All served with their famous fries and gravy.
Be sure to know that you'll likely be waiting in line for a while. Even if it's 3am in the morning on a Sunday this place is still packed. The service isn't the best and they do make you pay first before you get your meal, but who cares it's all about the poutine here!
If you feel daring enough they do host some poutine eating challenges from time to time. If you want to give yourself a personal challenge, try to finish a large T Rex on your own. I did and I quickly passed out of a food coma afterwards.