Pref Setter is an application used to edit plist (Property LIST) files, geared towards viewing / editing Mac OS X's preference files. Very useful for setting those "hidden" preference settings that aren't available directly in an application. While the emphasis is on editing preferences, Pref Setter is a general plist editor.
Pref Setter makes accessing your preferences easy with the "Open Domain Quickly" window, listing your preference files and those in the /Library/Preferences domain.
Preferences are also easily searchable, with the Find panel that will search all your preference files for a term, or search individual plist files for a term with the search bar in the document windows.
Pref Setter also has comprehensive copy & paste / drag & drop support. You can paste / drag an XML string (in property list format) onto a document window to create or change a value. And now, you can paste / drag a "defaults write...." string into Pref Setter and have it take care of writing that for you. No need to take a trip to the terminal!