I'd say it's a toss-up between Christmas and Passover. I know it's a weird combination, but hey
Christmas has just gotten waaaaay too commercialized. When I was little, it was about going to church, Santa and presents, and a family get-together. Now the Christmas decorations come out around October and it's all about spending money and making sure your kid isn't the only one in the neighborhood without the hot new toy.
The trouble with Passover is that I have to spend it with my in-laws. They are nice enough people - when taken in small doses with copious quantities of adult beverages. Last year my in-laws invited themselves to our house for the first night of Passover and demanded that we go to them for the second night - not one, but
two fabulous back-to-back nights of dealing with my mother-in-law. She and I weren't on speaking terms for a while afterwards...