Comment on OnyX

There are a great many GUI wrappers of defaults/pmset/nvram/sysctl and other command line tools, but this is one of the best. It is safe (doesn't do things you don't explicitly tell it to, and it de-authorizes itself on quit, so there isn't a lingering do-anything permission laying about. Recommended over Cocktail, MacPilot, Snow Leopard Cache Cleaner. And, it's totally free!