Ever seen these guys?
 

They are called improv Everywhere....they do some pretty neat things. I watched a few where the did slow motion shopping at home depot and "froze" grand central station.

http://www.youtube.com/watch?v=jwMj3PJDxuo <--Grand central station

http://www.youtube.com/watch?v=4vsdtCuXS_I&NR=1 <-- a "suicidal" jumper.