Hmm… most of the holidays I've employed are fairly mundane. I think the most unusual one so far is the observance (hard to call it "celebration") by one religion of the day their god abdicated. Not the sort of thing most sects add to their calendar.
Mostly, the world I am writing about is apathetic to religion and, though religion is the basis for many of their holidays, the religious context is lost on many of the people partaking in it. There are also no seasons in this world. So, for the most part, holidays are an excuse to take off of work, give/receive gifts, and get drunk. I do have one festival, though, not quite a holiday as it is far from annual, but a celebration of sorts all the same. The Coronation - the crowning of the new Royal Father. Since the line of royalty isn't hereditary, it is quite the elaborate process, and it is a week long (six days) celebration. The first day is the day of mourning for the deceased or lost Royal Father before, as nothing but death or presumed death can lose a king his throne. The second day is the day of choosing, where men and women across the country come to the capital and those qualified to be Royal Father (or Mother, rare though it is) are selected from the group. This is an age restriction (pubescent, or post-pubescent), insurance that they are not related to any member of the Advisory, some literacy tests, etc. Just to make sure they can act on the duties of the Royal Father. The next three days are spent in a death match between all qualified contenders, with the last man standing as Royal Father. The sixth and final day is the Coronation itself, where he is crowned the Royal Father, and all that comes with the position.
Nope. And don't imagine that it hasn't disturbed some of the other religions that his followers still seem to receive divine favor.…
(Unfortunately, the backstory necessary to explain the situation would require my summarizing a large chunk of 113 pages of the world's history: the event occurs around 66k words into the relevant document. All of which is backstory. When I said before that I'd constructed a complete world prior to setting a single story in it, I wasn't kidding. Well, that isn't quite accurate: I don't regard it as "complete" yet.… )
In one of my worlds, the people of one city celebrate the Festival of the Wolf, which is basically a midwinter festival. It's twelve days long and consists of twelve races and a wrestling tournament. The wrestling tournament is a spectator competition for which there is a monetary prize. The races are a bigger deal, but a bit more difficult to watch because they're races. The racers are the toughest, hardiest citizens; for each day of the festival, they must race to a sacred spring in the mountains and back, a twelve mile round trip, in what is often very bitter, cold wealther. As they run, they wear wolf pelts. At the spring they are given a ribbon (officials giving these out just stay there for the whole festival); at the completion of the race the first 20 back get a wax seal attached to it; to enter the final race on the twelfth day (also the day of the wrestling tournament final), a runner must have eleven ribbons with wax seals on them; they're sealed on one side with the king's official seal and on the other with the runner's, so they're non-transferable. The first back on day twelve is the winner, and is the guest of honour at the evening's feasting in the palace (the wrestling winner is a secondary guest of honour, but the winner of the race takes precedent). They also get a monetary prize of twelve Silver Wolves (a type of coin; the total prize is roughly equivalent to half a year's wages for an unskilled worker; about £7,000 or US$10,000.) All runners who complete the race on the last day are also invited to the feast.
The last day is really the big important day; there's a procession, carrying a lifesize model of a wolf made during the year by one of the guilds of the city (Potters, carptenters, metalworkers, teachers, masons, tailors, butchers, bakers, candlestick makers, etc) in a way which reflects that guild's specialty - easier for some than others, admittedly. There's music and dancing, and people dressed up; people in generally wear masks designed to looks as scary as possible. There's a lot of drinking. In terms of food, it's mainly meat and bread, with hog roasts and stuff. Mostly the colours used in the flags, bunting, streamers and other decorations are silver (or white where they aren't using metal), red (sort of the civic colour) and dark grey (like a wolf pelt).
The whole festival starts on the shortest day of the year; so by the last day, when all the big stuff is happening, the days are starting to get longer again. It's a celebration of defeating the winter, of living through it, but also of their civic pride and living up to their reputation of being remarkably resilient and tough even in the cold of the winters they get.
I can't even remember how I came up with it. I guess I wanted a midwinter festival that was a bit different from the Christmas clones you sometimes get. Winter seems awfully long if you don't have something to look forward to; that, I think, is why January is often more grim and depressing, and seems to drag on much more, than December. I also wanted to make an ideological link between this city, Hurreton, and Rome; the symbolism of the wolf was the obvious choice.
I don't have very freaky holidays. For most of them I have terrestrial models. Ancient Sumer is very inspirational.
My freakiest, well the only freaky thing about that holiday is the date it is held. Gevrit is a god of fate and gambling. The date of his next year holy day is chosen by random at the celebration of the current Gevrit day.
I tried to make that cult as random as possible. Many things are "diced out" or however you want to put it on that day. Even the hierarchy in the temple is overthrown and regambled then. Those who want to lead a especially Gevrit consecrated live chose a partner on that day at random. (Maybe till the next Gevrit day. I have not decided that detail yet.)
And of course it's a great day to gamble in general.
I haven't thought about this but I think that I should have some. I have a nomadic people, who may well celebrate the death of a person, maybe even a ritual suicide so that they are healthy enough in mind and spirit to continue the nomadic life after death.