I lost track of my stash of pads and tampons that I used to keep in the bathroom and throw in go bags and riot kits. If you had to bum a pad/tampon off a comrade unexpectedly what products would you prefer them to have? Pads? Tampons? any particular brands? I figure about 50% of everyone needs them ~25% of the time so after water, candy, and 9mm rounds it's one of the most universally applicable things to have handy.
Echoing the other commenter, I'd look for something like Always extra heavy overnight pads. Lifesavers when someone expects to lack access to facilities for several hours.