I personally do not think there is a non-cruel way to 'stun' mice. Stunning implys that they'll wake up again eventually. However I have no qualms about feeding 'fresh killed' mice. When you kill a mouse through cervical dislocation or by smacking it on a hard surface, the mouse is dead, but the nerve impulses will still cause the mouse to twitch and kick for a while so it still looks alive. This movement will often get reluctant snakes to feed without the danger that the mouse will suddenly take a bite out of them. I think when most people say 'stunned' they really mean 'fresh killed' and if the mouse DOESN'T die and wakes up again, they're obviously not doing it right and yes I think that IS cruel.