Couple of places on Yonge Street, that are decent, Eggspectation is pretty close to the HHOF, Richtree Market is right around the corner, you can get anything and everything there. The Royal York for something more upscale.
Sneak on an airport-hotel shuttle. A number of downtown hotels share a free airport shuttle for guests, just say you are staying at the King Edward or Royal York. I've done it before. How are they to confirm if you haven't checked in yet (assuming they haven't started calling each hotel to check if people have reservations).
As for other suggestions, go for a tour of the Steam Whistle Brewery if you've got time before the game. It is right next to the CN Tower (south of the CN rail tracks).
The airport rocket to Kipling station is definitely a popular choice. A cab is about $40, and will take about 25 minutes.
So you start at Union Station (between Front and Bay, and Front and York)
About 5 blks East is St. Lawrence Market - an old institution here in TO. If this holds any interest, you could come walk around and engorge yourself on various meats, cheeses, etc. It opens at like 5am on Saturdays. http://www.stlawrencemarket.com/shopping/south.html
Back at Yonge and Front is the HHOF. Easy.
About 7 large blks west of HHOF is the Rogers Centre. About a 5 minute walk. If you want a little variety, maybe walk down to the Lake (Queens Quay) and walk west along there, then you can walk back up (Rees St) for the game.
Are you going all the way to TO just for one day? Or is this a stop-over type thing?
TTC is super easy (and cheap!) from the airport to downtown, so that's probably your best bet. If it's just for one day, however, you may want to consider the Airport Express: http://www.torontoairportexpress.com/ Not sure if the extra $ is worth it though -- it may or may not be faster given the time that you'll be travelling (basically, rush hour both ways).
P.S. Don't forget to buy a hot dog from a street vendor while you're there
Toronto - best way from airport to downtown?
