I've always loved the Autumn atmosphere, when the weather cools down just enough to be comfortable in a jacket, and the trees all change colors. It's gotten so much better since I moved to Ohio; Nebraska still has Autumn, but in the west where I lived it wasn't anything special. Here, though, it's so nice... lots of rain and cloudy days, and the forest just explodes with reds and yellows and oranges and browns. And the squash are coming into season, and apples are in season here now too, so I can do things like make butternut squash soup or baked yams or baked apples with brown sugar and cinnamon. I miss that during the summer when I can't turn the damn oven on because it's already 89 degrees in my apartment even with the air conditioner going full blast.
I guess all that's my substitute for costuming and getting candy, now that I'm too old for that stuff. I'd give out candy, but I live on the third floor of an apartment, so nobody comes by.
Oh, and yes, watching shitty old horror movies is always a great thing to do too. Drink beer, eat roasted pumpkin seeds, and either watch stupid shit like Child's Play or maybe some old black and white classics. Everyone loves that.