There are too many to name all of them, but here is a list of ones that I have personally been to;
Niagara Falls, Ontario is impressive, but loses it's lustre after multiple visits.
Banff National Park in Alberta is the most beautiful place I have ever been to. Mountains, rivers, a hotel surrounded by wildlife and magestic views, and a gondola ride above the trees are reason enough to visit.
Toronto, Ontario itself is a cultural mecca and the site of many movie filmings.
Prince Edward Island was the setting of the famous 'Anne of Green Gables' and 'Road to Avonlea' books, films, and tv shows.
Peggy's Cove, Halifax, Nova Scotia is gorgeous. Also, they have a neat Mariner Museum that held a Titanic exhibit when I was there. It's was awesome.
Anyone who has been anywhere famous in Canada, feel free to add to this list. The world needs to know that we don't all live in igloos.