My family and I live in the Rexdale area, about a thirty minute drive from the core of downtown Toronto. I've (of course) been to many places around the city, and here are my top recomendations for visiting the city.
If you enjoy nature and light walks like me, High Park is a beautiful place to go. It's very large and has many different areas, paths, ponds and rivers, et cetera. It especially beautiful if you go in the spring during cherry blossom season, but it can also be very crowded during that time and the weather may not be the nicest. I suggest going on a nice fall day, when the leaves are turning red and it's sweater weather with a nice breeze.
Even though it's a bit of a drive outside of the city, I still highly recommend visiting it if rollercoaster rides are your thing. It has some of the tallest and fastest rides in Canada, and of course, the infamous 90 degree drop ride, Yukon Striker. I especially recommend going on a non-holiday Monday or Tuesday if possible, as weekdays are the least busy and you can easily get on quite a few rides with short wait times.
If you're visiting Canada for the first time and have a morning to spare, I would suggest visiting this lesser-known attraction. It's a really fun way of seeing the whole country, all in one day! It only takes a couple of hours to see, and it's very fascinating if you're interested in things like that.
This is not a surprise, as likely every tourist blog about Toronto would tell you to visit CN Tower. But honestly, it's worth it. Especially if you go for a dinner at the 360 Restaurant. It's the best way to see the city and an experience you'll remember Toronto by. And, if you do, I dare you to do the EdgeWalk!