Consequences is a game, played using only paper, pens, and some friends with fertile imaginations, which is very useful if you are stuck in a classroom at lunchtime because it's raining outside.
It is also a fun game to play if you are drunk, but obviously you need to be sober enough to be able to read, write, and follow simple instructions.
Each person is given a piece of paper and a pen (or napkin and eyeliner pencil, depending on the situation). Then they each write down something, fold the paper over so that what they have written cannot be seen, and pass the paper on to the next person.
The aim of the game is to produce a short story, which hopefully turns out to be funny1.
Here is the basic outline of what has to be written. Words in bold must be written, words in "quote marks" indicate the type of thing that should be written.
Once the end is reached, each person unfolds the paper they are holding, and reads it out loud to the group. Cue fits of giggles, and arguements about who wrote what.
Tip: the best names to use are those of famous people, historical charcters, or people present (as long as they're not easily offended). Quotes from films/books/famous speeches are good for "he said" or "she said" and it's often funnier if anything rude is implied rather than said straight out.
Another game with a similar theme, but a much larger scope, is Chain Stories