Everything! It's my favorite holiday, I love it so much! But I'd have to say my favorite parts are...
1. Dressing up in really fun, scary, and creative costumes.
2. Going to Halloween stores and haunted houses and stuff, and driving around and looking at other people's awesome Halloween decorations outside their house.
3. Partying with my friends. (Duh.)
4. Watching my favorite Halloween movies!
5. All the creepy aspects of it.... I just love everything about the holiday!