I used to keep my Walther in my nightstand on top of a leather case. One night I spilled my glass of water on the nightstand and did not do a good job cleaning it up. The water leaked into the drawer, wicked up through the leather case to my pistol, and completely fucked up the finish of the gun. It cost me two hundred dollars to get it re-blued.
Two things I learned
-Never keep your gun resting on leather; if it gets wet, it eats right through the finish
-Never have water on your nightstand if you keep your gun in the drawer.