My pick is the Nightmare Before Christmas. Is it a Christmas movie? Is it a Halloween movie? Both. It's both. The songs and the stop-motion animation are captivating. I just love that movie, and I'll use two separate holidays as an excuse to watch it!
I LOVE Nightmare Before Christmas! When I was a teenager, I convinced my family to watch it with me. They were not impressed by it and my mom found it downright disturbing. Since then, we've steered towards classic family holiday movies. But the year we watched Nightmare Before Christmas will always be a fond memory of mine!