I don't normally add much to the cameras besides what the manufacturer put on them.
Half case or Arca-Swiss type tripod plate.
I prefer the half cases where the strap attaches to the case. It saves a lot of wear on the camera. When I need to take it out to use on a tripod, the strap is superfluous in that siutation anyway. That's when the Arca-Swiss type plate goes on.
Lately I've taken to adding some "Mint camera armour"
https://www.bhphotovideo.com/c/prod...on_black_carbon_camera_covering_material.html
I place these on the camera top where the strap would rub.
For example, the M6 and M7 have little plastic rub strips to protect against strap wear above the lugs. My M2, M3, M4-2, and M5 are missing these. I've put them in using the Mint protector. I also use them on the top plate of the cameras without a built-in meter, to prevent meter marks from showing when I put on the Leicameters.
Final protection spot is under the wind lever, on the rear vertical surface. Prevents thumb wear from showing on the metal or black chrome there.
Oh yes, if you're one of those that don't want the Leica logo to show, then you can cover it up with this material also.