I'm not sure if we have anything that would be considered iconic nationally, certainly not in terms of influence or imitation.
However, styles strongly associated with the city and province would include:
1. Colourful clapboard rowhouses. These are found just about everywhere around the North Atlantic, from the United States to Greenland to Norway to the Faroe Islands.
October 20-22, 2017 by
R C, on Flickr
2. Rural saltboxes with a haphazard layout. The nonsensical urban form is kind of unique for North America and tends to be popular with tourists in that the towns that strongly exhibit this form are also the most popular for visitors.
Bonavista by
R C, on Flickr
3. The suburban style of Churchill Park. It pre-dates Don Mills, and a lot of its attributes were added to Don Mills, attributed to Don Mills, and from there were imitated around the country. Beyond the obvious features of suburbia (larger lots, driveways, a blend of SFD and rowhouses, streetcar configuration, etc.), it's most notable today for the corner windows (which wrap around the other side of the house, of course). It was also developed by a crown corporation.
In terms of individual buildings - none, in my estimation. Cabot Tower is probably our most well-known but not for any architectural reason. Fortis Place is probably our most interesting highrise, especially given its use of wood, but it's not well-known.