Windows only: If you've got an application with a really ugly icon, or you just want to get some hard-core nerdy action with your desktop customisation, Resource Hacker is the tool for the job.
Over at the Tweaking with Vishal website, he's put together a brief guide to using Resource Hacker to customise and replace graphical elements like icons, bitmaps, cursors, or even rename menu items for almost any Windows application.
If you've paid attention to our Featured Desktop series, you've probably noticed that some of the really hard-core desktop customisers, like reader nitzua and his million years of Litestep desktop, have gone the extra mile and used Resource Hacker to replace icons, and other graphical elements, from their favourite applications. If you've ever wondered how people manage that level of customisation, this is exactly what they are doing.
Of course, this isn't the type of thing that just anybody should attempt, because modifying system files or hacking your applications is likely to cause things to break, especially if you aren't sure what you are doing. Still, if you are willing to tread into the dangerous world of hacking stuff to create a sweet desktop, Vishal's tutorial (and a good backup software) is a good way to get started.
All About Resource Hacker in a Brief Tutorial [Tweaking with Vishal]