Thanks to a comment, I found out about Gadino's Pizza in Kitchener. A couple weeks ago, I called them to order a pizza: yes indeed they make gluten-free pizzas and I got to taste one first hand.
I can't honestly say that the crust was the best pizza crust I've ever had (it was pretty tough at the edges), but overall it was a great pizza. And ordering in pizza is such a treat for Celiac's that I was pretty ecstatic. I'd definitely order it again!
I tried to ask a few questions about their toppings but unfortunately I don't have too many tips to share. The man I was talking to didn't know if the pepperoni or ham was gluten-free. I stayed away from both of those toppings, but he said other customers haven't complained of any problems. If you find out more details, feel free to leave a comment.
He was a very nice man though - I think he might have been the owner. He even called me back about 1 hour later to see how I liked the pizza.
Here's Gadino's phone number once again: 519-579 2901.