It's amazing how much fun one can have hanging out at Walmart for hours at a time. At 2am, some of my friends and I had nothing to do. Starting in the grocery section, we made our way around the entire store messing with whatever free merchandise was around to screw with.
A word of caution... Turning a can of air upside-down and spraying it on your friend can hurt their skin. I have experienced this a few hours previous, and my skin still feels tingly and some of the skin is flaking off, so be careful. :-P
Anything from throwing footballs, to playing video games, to putting motorcycle helmets on and have head-butting contests can be enjoyed at Wal-mart. My advice to all those who can't sleep and are bored. Call up a friend and go chill at Wal-mart. It's cheap, makes for good stories, and you could very well have a time of your life. :-P