Origin of "Trick or Treat"
Not a very common one, but anyways; consider the Canadian regional Halloween Apples!
In some parts of Canada, children sometimes say "Halloween apples" instead of "trick or treat." This probably originated when the toffee apple was a popular type of candy. Apple-giving in much of Canada, however, has been taboo since the 1960s when stories (of almost certainly questionable authenticity) appeared of razor blades hidden inside Halloween apples; parents began to check over their children's "loot" for safety before allowing them to eat it. In Quebec, children also go door to door on Halloween. However, in French speaking neighbourhoods, instead of "Trick or treat?", they will simply say "Halloween", though in tradition it used to be La charité s'il-vous-plaît ("Charity, please"). Wikipedia
Alternately, consider the suggestion in my comment above, Curse or Candy!
Children go from place to place and say "curse or candy!" Heppy Halloween