I used to work in a deli in a grocery store. I hated when customers would be on their phones! I walked away from one once, and when she motioned me, with a glare, to come and help her, I said, very loudly and succinctly so the person to whom she was talking to could hear, "Oh, I just wanted to make sure you were done with your conversation first." Of course, you say something like that with a smile, and they can't help but feel sheepish. She quickly said, "I have to go." and hung up. It was a "so what did you think of XXXXX's dress? Wasn't it ugly?" type of conversation.
The other one that gets me is in church during services. Come on! Turn the dang thing off! Also in church, are remote starters for cars. A lot of them beep. There is nothing more annoying than hearing that beep during the last hymn. Can't you wait until announcements are over? Yeah, your car may not warm up to the point you would like it, but dang! Maybe take a little more time to talk to people on your way out.
The other place for cell phones that really gets me: theatres. Not movies, but plays. We don't get out to the movies very often, but we do save up to go see a good play every now and then. I feel bad for everyone in that circumstance. But I cannot help but feel smug as an usher comes down and escorts the person out... Or if it's a high school show, I just plainly feel bad for the kids. There is usually an announcement before the play to turn off everything that could make a noise.
When we directed plays, we used to take out our cell phones for distraction rehearsal and make them ring and would mimic a crying baby, etc. Heck, one time we really went over the top and moved around the set while the rehearsal was going on. But still, I don't know if every director just does that as a matter of course.
edited for gross negligence in grammar. Good grief! I'm supposedly an English teacher.