Lucky! I wonder if it's the emulator for me...
A nuzlocke challenge is a different way of playing a pokemon game. There are three main rules: If a pokemon faints, it is dead, and never can be used again. You can only catch the first pokemon you see on every route, if you fail to catch it, tough. And you must (well should) nickname all your pokemon.
I've never done one before, but it sounds difficult and a lot of fun. I've been thinking about trying it out on silver if you want to be my companion on gold? :P