Chewing gums
Chewing gums. I hate those for two reasons:

When one chews, then looks disgusting. I also do not like to feel the breath of a chewer. So called freshness. It makes me feel incomfortable. And when chewer is done with a gum, he or she spits it on the floor or even puts to a place, where nobody can get with their eyes, but certainly will get with their hands. Yes, hands. Sometimes, when I touch a downside of a table, I feel something sticky. Nice. Well, it's not the reason number two however. Number two is, when I walk, I suddenly start to feel, that it has become not comfortable to step and not so easy to lift a leg. And then I look at a sole of a shoe to find out, what's wrong. Well, no comments needed here, I guess.