MIT Mystery Hunt

The MIT Mystery Hunt is an annual puzzlehunt held on the MIT campus. Teams are required to solve puzzles, the solutions of which help to solve the meta-puzzles, which then help to solve the meta-meta puzzles, and so on. There are also many events that take place on the MIT campus. The goal of the Hunt is to use the solutions to the puzzles to help find a coin of some sort somewhere on the MIT campus. Early Hunts were around 30 puzzles long. They have since grown to be around 100 puzzles long, with 10 to 20 meta-puzzles. The winners of the hunt gain the right to design the next year's Hunt.

The hunt is unique among many puzzle hunts in a few ways. There is no cap on team size, leading to a lot of really large teams participating. Also, most of the puzzles for the past few years have been available online, meaning that people who couldn't go to the MIT campus could still participate.

Hunts often come with a plot to explain why people are going around solving puzzles. Past plots have included a murder mystery, a journey through hell, and a 30(0)th anniversary celebration of the Hunt.

An intro to the Hunt can be found here. The Hunt is held every January during Martin Luther King Jr. Day weekend, beginning at (around) noon on Friday, and running continuously until a team recovers the coin, usually 40 to 50 hours later.

Beware, the example list spoils the solution to many puzzles. If you want to solve them on your own, please don't read it.

Tropes used in MIT Mystery Hunt include:

Alternate Reality Game: While it did originate as a non-web puzzle, it is now primarily a web hunt with non-web components (i.e. the kickoff, the MIT campus runarounds, endgame and wrapup).
Blessed with Suck: Congratulations! You won the Hunt! Now design next year's Hunt!
Excuse Plot: The reason teams are solving puzzles. "The path through the Mushroom Kingdom is full of puzzles." You don't say.
Expy: Not of characters, but of puzzles. Every year there's at least one "tons of tedious and confusing but technically unambiguous directions about modifying a sequence of letters" puzzle, as well as a puzzle involving box puzzles (such as nurikabe or thermometers). Puzzles containing smaller Mystery-Hunt-style sub-puzzles are also popular.
Good Name for A Rock Band: The solution to Toto, I Have a Feeling We're Not in Kansas Anymore requires the solver to recognize the pictures are referencing rock bands who took their names from movies.
Guide Dang It: And how! The entire point, really, is that you're supposed to figure all this out as a team. Also, there is no guide until the end.
Moon Logic Puzzle: And how! Several puzzles require you to take....interesting trains of thought.
Only Smart People May Pass: And how! Topics you may need to know include:
Sequence Breaking: Examples of this played straight and averted: In individual puzzles, you can often figure out the solution without figuring out all the pieces, by inference. You can also often solve meta-puzzles without figuring out all the solutions to their component puzzles. However, you can't find the coin early by accident; the organizers will not put it there until someone's gotten to the point of doing the final run-around.
Shout-Out: Nearly every single puzzle contains pop-culture references...which you ~~probably~~ need to know to solve the puzzle. Arguably this detracts from the puzzles as simply never having heard of some obscure webcomic or other that the designers love may well stop you dead.
Viewers Are Geniuses: See the Only Smart People May Pass entry above.
Wiki Walk: Finding the solution to Walkthrough from 2011 requires you to do this.