I think I can top everyone about this matter. I was at a restaurant with my new boyfriend, it was a romantic meal and we were both looking forward to a 3 course dinner with wine and desert. Our appetizer came, which took way too long but as the conversation was good, we didn't say anything. We enjoyed our wine. An hour later, with no main course in sight, my boyfriend called a waiter over and suggested they may wish to hurry up and bring us our entree. There had been some couples who had arrived after us and had already eaten and left. The next thing we new is that our bill arrived, for the whole entire meal! We were shocked and went straight to the kitchen. The waiter told them we wouldn't pay our bill but we said, we didn't even get our entreee but were charged for it. In the end, the boss said he was sorry for the mix up and we did not need to pay for anything. Then we got fries on the way home!
Sounds similar to what happened to me, once.... I had gone to a restaurant by myself with a good book to read while I ate. I had received my food ok, but at the end of the meal it seemed to take forever for the waiter to come back with the bill. He had also never came while I was eating to ask for refills or dessert, but since I was so engrossed in the book it didn't really bother me that much. I actually thought that perhaps he saw I was reading and was trying to be considerate by not interrupting my reading, so after several long minutes of sitting with the empty dish in front of me and no sign of the waiter, I just marked my page, closed my book, and looked around for my waiter. After another long bit of time had passed, I finally yelled "Excuse Me!" to flag down a waitress in a different section as she passed by my section. She came over and I explained that it was now over an hour since I had last seen my waiter, and that I was ready to get my bill and leave. She left (presumably to get my waiter) and came back shortly with the manager. The manager, being extremely apologetic, had told me that my waiter had actually left early claiming that all of his tables had been taken care of. Because of my long wait, the manager comped my bill completely. As I was leaving, I gave the waitress a tip for helping me out even with my frustrated attitude.
Thus, I'd have to say my biggest pet peeve with restaurants are inattentive wait-staff. Whether it's simply not refilling pop / coffee in a timely fashion, or something more drastic like Penwoir's and my situations.