I see there are already some pizza suggestions on here but BONA PIZZA is exceptionally good and has a wide delivery range: http://www.bonapizzapasta.com/

If you are stuck near the touristy area the best option, imho, is GURU. It's fine dining Indian food with many vegetarian and vegan options, as well as the standard meat options. The food is well spiced and delicious --much better than I would expect to find near Clifton Hill and good enough that I would even recommend it as a place to go if in Toronto. On Victoria Street across from the Casino.

But I would also highly recommend getting away from the agglomeration of hotels and wax museums to go to the downtown area. North of the tourist area cheaper, better food and more laid back. At 4337 Queen Street there is a charming place called Mide Bistro, serving up fresh, gourmet food that is fantastic for vegetarians and non.