colorFLASH Visitors can change the background color of the page by running their mouse over the word of their choice. Over fifty colors to choose from. http://www.geocities.com/j32926/flash/flash.html
HoldTheButton.com Times the visitor's ability to hold down a button and allows the results to be emailed to other people who are interested. http://www.holdthebutton.com/
Neall's Nonsense Button Featuring a button that's a bit pointless. http://nsbutton.gq.nu