BlogTo has a list of 10 of them, here, and I have to say, they did a good job. I am in full accord with Shawn Micallef on the need to blow away all the building on the North East corner of Yonge and Bloor. No one would shed a tear for replacing them. As for me, the ugliest building — and it was close — is the Bloor Dundas Square (shown above). That monstrosity has been around forever. Pretty much anything would be an improvement on what is there now.
Toronto has many great buildings. These are none of them. 🙂