hammer, chisel, gloves, goggles. If you have a multi tool you can grind out some of the grout first then get the chisel under the edge. Start to tap under the tile until you get one loose. That gives you a place to start with. Make sure you angle the chisel with the back of the tile or you will punch holes in your drywall.
Start at an end and push a stiff putty knife against side and tap with hammer. Keep chipping away. Won't take long once started.