One habit I really hate is spitting casually in the street/pavement. Discreetly when required yes, but just lobbing it on the pavment as people walk past is a no no.
Seems to happen a lot in Leeds. Not noticed it quite as much in Brighton though.
Due to a biuld up of saliva which if not cleared will effect my breathing when I go training, same reason why you see footballers do it all the time on the pitch.
I must note I never spit on the pavement, always into the road or down the drain.