1. Uninvited people overstaying their welcome. You just randomly bump into this one person you barely know and have a conversation for a few minutes, then when you say your goodbyes and think you're going to get back on schedule, the person just has to have a bright idea and fuck up the plans with his/her own plans.

2. Going to a restaurant and your friend says "I'm not that hungry", but end up eating their food, then eating yours. If you're hungry, just say so! I don't mind if the person wants to try it, but don't sit there and tell me you're not hungry.

3. Cashier problem would be the customer coming in, you tell them the price, they say it's cheaper over there and complain, then end up buying it from here anyway.