Of course the obvious, straps.. But also..
travel cases, I have a nice 3 watch roll from Underwood, nice leather, nicely built. Another is an Oakley watch case, it just holds once watch, but it doesn't look like a watch case, and it fits nice and snug in the gym bag! Then there is the shrine, winder, watch box, and little glass dome that holds an antique pocket watch.. All fun to have!