TinkerTool

[Zammy-Sam]

TinkerTool by Marcel Bresink allows you to access user settings built into Mac OS X that cannot be controlled by the standard "System Preferences" application. The best feature is to unhide hidden files and folders and quit the Finder.app.

 

[Satcomer]

TinkerTool gets my vote too.

 

[Jeffo]

I use it too, but mainly to relocate the dock and give it a shadow and use a faded icon for hidden programs.