Best: Halloween falling on a Saturday when I was a kid in the early 80s. My friends and I started trick-or-treating at noon and didn't stop till 7 or 8 PM. We actually had to go back to our houses and empty our haul bags so we could re-load. Our feet were sore but the haul was worth it!!
Worst: Last year my area was hit by a freak snow and ice storm two days before Halloween, which took down a lot of trees and power lines. Parts of town (including my house) had no electricity for four days and our town cancelled all Halloween activities due to the amount of debris on the roads. So my kids were bummed that they didn't get to go trick or treating in their cool new Mario Brothers Halloween costumes. :(