Post I accidentally put in the under 100m thread. Duh.
For older buildings I really like Sun Life in Montreal.
More contemporary, I really like Tour IBM. A couple of local (Calgary) favorites of mine are First Canadian Centre (take note, FCP - this is how you make white marble scrapers look good!) and Nexen...considering these two were built in the early 80s, they really are outstanding buildings for their time. Nexen looks like a brand new building.
http://en.wikipedia.org/wiki/First_Canadian_Centre
http://en.wikipedia.org/wiki/Nexen_Building,_Calgary
Of the many skyscrapers recently completed, or about to be completed, I love the new RBC tower. Particularly interesting since I distinctly remember the original Royal Bank building was the first skyscraper ever to catch my interest, back when I was in TO at the age of 12. I'd put Woodwards right up there too. The next couple of years are going to be really exciting as a few other brilliant-looking buildings are completed...Bow, Ritz-Carlton, Maple Leaf Square, and possibly Eighth Avenue Place have much potential.
But sorry guys, I absolutely despise First Canadian Place. In fact it's the only one of TO's bank towers that I DON'T like. I really hope something taller goes up right in front of it, just so I won't have to see it in the news and on SSP so damn often!