my landlord doesn't return my deposit, what do i do?

From now on, you should be aware that landlords cannot lawfully ask for a key/damage/security deposit of any kind, except for a deposit of last month's rent. You should never pay them such a despot in the first place, because it's aggravating to get the money back should they decide to withhold it.

I'd say your best course of action is to keep emailing, texting, and calling them until they eventually return it. Let them know it's a priority for you. If it helps facilitate the process, offer to meet him somewhere convenient to get the deposit back.

If he blatantly refuses to return it, and you feel like going through the rigmarole to get it back, you can file one of these, but it's not free:
http://www.sjto.gov.on.ca/documents/.../T1.pdf?b58864

Yeah, the only deposit they're allowed to ask for legally is the last month's rent, and then when you get to the last month you don't have to pay it, since you already paid for it up-front. This eliminates any issues in terms of getting the money back.

If it's a different kind of deposit then obviously they should return it, but since it was an illegal deposit in the first place I'm not sure what the legalities are regarding getting it back. While you're at it though, you should also try to get a receipt for everything you paid your landlord, because you'll need it if you get audited by the CRA.