For Toronto:
1. CN Tower (John Andrews, WZMH Architects)
2. New City Hall (Viljo Revell)
3.Gooderham Building (David Roberts Jr.)
4. Old City Hall (E.J. Lennox)
5. Toronto Dominion Centre (Mies van der Rohe)
6. Maple Leaf Gardens (Ross and MacDonald)
7. University College at the University of Toronto (Frederic Cumberland and William G. Storm)
8. Royal Ontario Museum -ROM- (Pearson and Darling, with first addition by Chapman and Oxley and newest addition by Daniel Libeskind)
9. OCAD Sharp Centre for Design (Will Alsop)
10. Ontario Place (Eberhard Zeidler)
11. Robarts Library (Mathers and Haldenby)
12. Gooderham and Worts Distillery
13. Casa Loma (E.J. Lennox)
14. Scotia Plaza (Mathers and Haldenby, 68 storey tower by WZMH Architects) at left
15. Fairmont Royal York (Ross and Macdonald)
Special mention: First Canadian Place (not very iconic, but the tallest office building), Royal Bank Plaza (distinctive 24 karat gold tinted glass facade), Union Station, Honest Ed's, and the CHUM building.
Edit: Under Construction or Proposed buildings shouldn't count. But in the future, 1 Bloor East and the Gehry AGO Project might make their way into this kind of list.