I use the UltraVNC viewer on Windows to connect to a Linux session. I spend 90% of my day working in the Linux session which uses focus-follows-mouse.
What I would like is the option to have the VNC viewer steal the focus in Windows when the mouse enters the viewer window.
For my setup I have two monitors, one of which is a fullscreen VNC viewer. Since Windows is click-to-focus I often have the case where I send an email in Outlook and then move my mouse back over the VNC viewer screen and try to start typing in a remote Linux window, only to have the keystrokes still sent to Outlook.