Earlier of this week we added 3 entries to the IOMBCC (International Obfuscated MSX-BASIC Code Contest) to our downloads database. One of these entries was Prime numbers, by Daniel Vik, a oneliner that caculates prime numbers. As of now, you can another oneliner from Daniel Vik that does exactly the same in a completely different approach: Prime numbers (2).
If you're wondering what's so special about these BASIC listings, you should probably have a look on how it looks over here. If you still need a definition of the term 'Obfuscated Code' after that, you can read this explanation. You can send your own entries in at this forum thread.
Relevant link: IOMBCC entry 9 - Prime numbers (2)