Writing obfuscated code is a favorite pastime of some Perl hackers. The basic principle is that the code should be as close to impossible to figure out by visual inspection as you can make it.
Closely related to obfuscated code is the game of golf: trying to solve a given programming problem in as few keystrokes as possible. The results can be, but are not necessarily, obfuscated.
Both types of "fun code" — obfu and golf — are suitable for posting in this section.
Some tips for writing/decoding obfu:
Word of warning, though: Don't be too cocky with your post — almost inevitably someone will post a reply that does the exact same thing in even fewer characters!