Document lickers.
I recall the beginning of the digital era was heralded by claims of the ultimate elimination of paper and the arrival of the "paperless office". I looked forward to this with great anticipation because it meant the end was near for the lickers.
I am still waiting.
I see people thumbing through a sheaf of papers and licking their finger every few sheets as they work their way through it. I even saw my doctor do it the other other day, which surprised me - but at least they were her files. I have always detested lickers. If a bank teller did it while counting out my money I would ask for "a new set of banknotes, no saliva, please".
My boss for twenty years frequently used to call me to his desk to go through some new document that had just arrived. He would read the relevant paragraphs out loud to me, depositing his saliva on the corner of every page as he went, before handing the document over to me (still wet), whilst I had to hide my utter disgust and go back to my work station and reluctantly work with it!
Unfortunately people still do it.
Licking is icky and unhygienic. It is a revolting, anti-social habit, akin to spitting in public and it can spread disease.