Rich Rittenhouse mentions beeswax and relief from irritation of the lips and alleviation of unwanted hair loss due to hiding of pluck points on covers, he also mentions the air seal effect of the stuff (BTW don't use so much that your harp looks like a legwax plaster, little is good, I keep telling my wife) Bobbie G uses the stuff to stop wolf whistles on Lee Oskars (the Wolf is the out of tune beating you get from two adjacent notes being slightly out of tune, on Lee Oskars it is due to something which Beeswax cures)
One further use is to improve tone on the harmonica, other peoples. The improvement is achieved by taking two chunks of BW and forcing them into your ears.
Truthfully ..... one point I would make about Rich's post. He mentions smile wax and the fact that you don't need a soldering iron, or somesuch, to melt the wax into position. I am talking chromatic here. The nature of the #270 harmonica for example, is such that all the parts of the slide movement, body and mouthpiece don't fit together mechanically well. The Bees wax fills in for bad workmanship. If you MELY the stuff into position you get a far better seal than if you PUSH smiley wax in. The reason is that there is obviously a far better flow further into the mechanism and more of the small leaks are sealed.
You can also use beeswax as chewing gum.. Great for in Maths class kids... "Take out that chewing Gum boy and put it in the trash can!!" " No need Sir, it is BW and I'm repairing my harp" " Oh, that's all right then"