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Bottom-Left activates Dashboard
Top-Right activates non-password protected screensaver (very entertaining when trying to procrastinate)

Exposé features like show all windows and hide all windows, as well as an application switcher and some iTunes controls are programmed to my mouse.
 
Can't stand em. I used a hotcorner last year to do a password protected screensaver, because anytime I left my computer unlocked, my roommates thought it would be funny to do various things to it. Coming back from a meal to tub girl as your wallpaper isn't the most pleasant thing out there, so I had to have an easy way to lock the comp. Still hated it because I would always accidentally move my mouse up there when I didn't want to activate it.

Now that I'm on my own, I don't use them and don't have to worry. I just have the Expose buttons mapped to my mouse buttons
 
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