I hate the a**holes who insist on smoking in underground subway stations. Even though the whole system is supposed to be smoke-free, at least once a week I find myself trapped underground with someone (usually a middle-aged or older man) smoking and filling the entire station with smoke. (In fairness to Germany, this may be more of a Berlin thing than a nationwide phenomenon.)
Relatedly, I also hate all of the Germans (also mostly older men, although there are plenty of younger ones too) who ride the trains and walk about the city reeking of that lovely combination of cigarette smoke and alcohol breath–perhaps with some B.O. thrown in. Disgusting.