Conveniently located on-site at Pearson International.
Made reservation on car rentals dot com for a premium class car from Alamo. That'll get you either a Nissan Maxima or Chrysler 300. $37USD/day.
Alamo and National share a counter, so I was very confused when the National agent offered assistance. Turns out they're basically the same company. Check in was quick, easy and painless. Agent points you to car, you jump in and go.
Same for the returns. As soon as you pull up, someone is there to give the car a glance over, check gas tank, ask if everything was ok and before you know it, you have a printed receipt in hand and you're on your way.
My only gripe with this rental is that the all-weather mats could have been a bit cleaner and the car had a slight odor. Signage at Pearson is horrible and it's quite a guessing game to just exit the airport, so good luck with that.