Suppose you're at a MacOS desktop and you need a VNC viewer (but eventually this parenthetical comment will say something constructive about Remote Access for Windows); this happens reasonably often. While there are several fine VNC clients for MacOS, my experience is their installation is a bit "fiddly". In particular, most (?) (now?) depend on X. For instantantaneous gratification--if you already have a wish installed, such as TclTkAquaBI--all you need are tkvnc's two source files. Fantastic!