Use Halloween cookie cutters to cut tortillas into shapes such as ghosts, goblins, witches, and jack-o'-lanterns.
Lay the cutouts slightly apart on 2 nonstick baking sheets about 14 by 17 inches.
Mix cheese and chili powder.
Brush tortillas with butter. Sprinkle with cheese mixture.
Bake in a 350° oven until golden and crisp, about 15 minutes; if using 1 oven, switch pan positions halfway through baking.
Transfer crisps to racks. Serve warm or cool.