Found this one on Hacker News, and thought that it might interest some other too:
http://en.wikipedia.org/wiki/Xor_linked_list

And here is the Hacker News thread with a great discussion about it:
http://news.ycombinator.com/item?id=3925883


Shitlord by trade and passion. Graphics programmer at Laminar Research.
I write blog posts at feresignum.com