Five Guys on St Catherines has some pretty great hamburgers. It's a nice and new location.
I just wish that they wouldn't pack them all to go. I found my burger gets soggy, and since I ate in on both visits, I would rather have just gotten it on a paper plate. They give you a mountain of fries, be sure to order the smallest order unless you have a huge apetite. While it is a little pricey, the quality is way above most fast food burgers. Definitely worth checking out if you're hungry and in the area.