Every few months I get asked how to do this, and have to go dig it up again, so I may as well post it here to save me the trouble of trying to remember where I posted it last.
You can configure Xsun to let you kill it with a keystroke, much like the Xorg and XFree86 servers. To do this, you need to activate the X Keyboard Extension (XKB) which extends X keyboard handling in a number of ways. (It's on by default in recent versions of XFree86 and X.Org releases, but not in Xsun since there are still some issues in the Xsun implementation and XKB keyboard maps to work out.)
To do this, add +kb to the Xsun options in /etc/dt/config/Xservers to start in XKB mode. (If /etc/dt/config/Xservers doesn't exist, create it with "mkdir -p /etc/dt/config ; cp /usr/dt/config/Xservers /etc/dt/config/" .)
Now login and run 'xmodmap -pke | grep Delete' - it should print a line like this, though the number varies depending on keyboard type.
keycode 83 = DeleteTake that line and feed it back into xmodmap with "Delete Terminate_Server" added to the end like this:
xmodmap -e "keycode 83 = Delete Delete Terminate_Server"Now pressing AltGraph (or the right Alt key on PC's) + Delete should cause Xsun to exit. To make it permanent, you probably want to stick the xmodmap command in your $HOME/.dtprofile or somewhere similar. You can pick other keys to modify if you prefer a different combination - though you probably want one that you won't hit by accident, are likely to press when you put a book down on your keyboard, or your cat decides it's time to get your attention by walking across the keyboard.