Shatner is well known, but I would suspect only in North America.
GSP is huge, and I am a huge fan of his, but he is only known in the MMA world, which is growing all of the time.
Celine is a mega power diva, like it or not, and she is very well known worldwide. She is in the same league as the Whitney Houstons, Adeles, or Mariah Careys of the world, and there really is not much more than about a dozen female singers who fall into that category.
I am not necessarily a fan of her music, but I am proud of her, as all Quebecers really should be.
Guy Laliberte is certainly mega-wealthy, and Cirque du Soleil is known world-wide, but I don't think the majority of people would know who he is.
Should anyone be considered who is not present-day, like maybe someone like Pierre Trudeau, or someone else that I am not thinking of? Arturo Gatti or one of the Hilton fighters? Rocket Richard? Mario Lemeux? Gilles Villeneuve?