A good Swiss Army knife, but only in your checked luggage.

Alcohol wipes or alcohol gel in a small 3oz. container is useful, and a good idea.

The old German method I picked up from a multitude of LH flights, was to carry a small bottle of 4711 spray cologne around as a travel sanitizer. This is what used to be given to the mariners on U-boats, rather than showering.

The high alcohol content worked very well, but you end up smelling like Limoncello.