How about a gag gift? His own personal washer and dryer. What you do is get the biggest box you can find, and at the top of all the packing, have a note to say (or put it in the card if he'll open it first), "Enclosed are your own personal washer and dryer. Enjoy!" or something like that.
Then you go down to the hardware store and get the biggest washer you can find. I mean, the kind in the nut and bolt section. Then you get a cloth and run it through the washer and hide it amongst all the packing in the box.
If he really has everything, this will probably give him a good laugh and that's better than something else he doesn't really need. :)