John Carpenter's The Thing. I don't know if I'd call it "unconventional", but it's the perfect horror film for Halloween. Alternatively, the 50s "The Thing" is good for some laughs, and for kids is still scary.
The "Monster Squad" is an excellent Halloween movie. Good for kids-through adults, and some fairly creepy moments. Also has the best WolfMan EVER! I'd put it in the same category as The Frighteners.