Walk along Queen Street East in the summer and there are *very* few places that have lines out the door. Ed's Real Scoop is one of the rare exceptions: it's always busy because they serve, without a doubt, the best ice cream in this part of Toronto.
The selection is great and every day or so the staff will put a 'suggested pairing' on the chalkboard. That suggestion is almost always good: its led me to try some chocolate chilli ice creams and try their burnt marshmallow. I've never been disappointed by following the pairing suggestion.
One special note: be sure to get a waffle cone. They actually put a little bit of marshmallow in the bottom of it, so that it doesn't leak any ice cream out the bottom. In addition to be incredibly practical it means that the bottom of the cone is a special treat!