Ok how about brainstorming some challenges that dont suck. Prefferably ones you can do alone because I kinda think its weird to go up to a chum and say "help me me do this stupid thing" "why?" "it's a challenge on the internet". It depends on how awesome it is though, if it's awesome enough it could turn out sick.
* Make a flag saying whatever you want, whatever size you want, and then scout out town for the highest building you could out it on top of and put it there. High buildings, big flags and cool text on 'em wins.
* 'Decorate' a common area with garden gnomes.
This one is pretty cool:
* Buy a big set of toy soldiers, some glue, then go around town and create epic toy soldier battles taking place on things, by gluing up the toy soldiers on light poles, steel bars, railings, dumpsters, whatever you can find. Pictures or it didn't happen. And make sure it's somewhere where people will notice it.