I hate it when people who are doing customer service work are engaged in private, personal stuff when they're supposed to be working: like shirking their duties to talk to friends on the phone, or making out with their boyfriend/girlfriend. For that matter, it bugs me when they're clearly not busy and are just standing around but still don't make an effort to talk to you. Mostly, it bugs me when people don't do their job. I don't hate, however, customer service reps who are doing their job by serving customers. It bugs me to no end when people who clearly haven't worked a service job in their life get irritated with servers over stupid, petty nonsense, and chew them out publicly even though they're only making themselves look silly. Suprise, suprise, giving attention to customers is what service people do, and if a server is absorbed with providing a quality customer service experience to one customer, don't interrupt or get irritated just because they aren't addressing you: the world will keep turning and, let's face it, you probably would have wasted your extra 2 minutes anyway.
As a bartender, if anyone on the other side of the bar snaps their fingers at me, waves, shouts at me, or otherwise cuts line, I automatically serve them last. I don't care if you're in a hurry: you wait your turn like everyone else. You don't want to be smalltalked? Great, I don't want to talk to you either, but I do oblige those that do want to chat because that's part of my job. Be pushy all you like, threaten not to tip, try to bribe me, threaten to talk to my manager, I don't care. First, the presumption that you're more important than everyone else is wrong. Second, I don't want your gratuities if you're a douchebag (although, in my experience, the rude customers aren't satisfied even if you break your back for them, and rarely if ever tip anyway). Not only do I not care if you didn't have a good time, I don't want you to come back to my bar if you're a dick because the other customers don't appreciate your behaviour, and if I shirk the good customers to serve the bad ones it reflects badly on me. People going out to have a good time don't want to be surrounded by pushy assholes, they go out to get away from the stresses of their lives, not to have self-important wankers inconveniencing them by disrupting service. I'd rather leave one person inconvenienced than inconvenience the whole group. You may leave unhappy and tell 10 of your friends that my bar sucks, but all the customers I've taken the time to serve properly are going to go off and tell a few of their friends how awesome it was, and at the end of the day I get more good press from doing a good job than I do leaving one or two people unhappy.