If you're a football fan visiting Calgary during CFL Season (generally June - November), go see a Calgary Stampeder's game. Tickets can be purchased at any Calgary Safeway store for $20 each. McMahon Stadium serves as a home stadium for the Calgary Stampeders, as well as the University of Calgary Dinos, The Calgary Colts, The Calgary Gators and the Calgary Wolfpack. The Stadium was also used to host the 1988 Winter Olympics opening and closing ceremonies.
As the fifth largest stadium in Canada, it can seat over 38,000 screaming fans, and promises an energetic and exciting atmosphere. There are plenty of concessions and vendors on site, but be advised that parking can be a real pain, so take the C-Train if you can. Go Stamps Go!
They call Flames Central a "Virtual Arena" for a reason - it's a sporting event viewing experience like no other. If there's a game on, and you can't be at the game, the next place to be is at Flames Central. However - that's not why I love Flames Central personally - for me, it is my favorite venue for live music in the city. They always have awesome bands playing, and it's a big enough venue to feel like a party, but small enough to feel really intimate if you're seeing one of your favorite groups perform.
I was also extremely impressed by their selection of local beers. Come for the experience - stay for the party.