There's a plugin for Firefox called Vimperator which is what it sounds like -- a vim style interface for Firefox. It has the curious ability to nearly remove the titlebar of the Firefox window. This functionality is accessed with vim-style commands.
Firefox with almost no titlebar
Does this depend on something special about Firefox or is it possible to apply this change to apps in general or maybe to apps that use a particular framework?
By possible, what I really mean is possible without modifying the source code of the program.