Rexall on Spadina is the pinnacle of convenience. It's 24 hours, close to the university campus, and close to restaurants. They have the usual selection of drug store items including snacks, toiletries, cosmetics, etc. I usually pick up shampoo and toothpaste here.
Most importantly, the pharmacy on the second floor accepts student insurances and bills directly for any prescriptions. They also give a discount if you keep the receipt and spend more than $25 the next time you come within certain dates.