I spent Mardi Gras working the bar, which was very full. My *favorite* customer of the night was a guy, when I was running around, arms full of glasses (even with the new shipment, we ran out of glass glasses), having just taken three orders, wanted to just give me his food order, and then got pissy when I flat out told him, "I'll come to your table when I'm finished filling the orders I've already taken, and I'm going to forget your order if you give it to me now."
Always gets me, when people think that their order is the most important, that all bartenders should stop taking the orders of people waiting longer, and get to their order now. Kenny, the jaded bartender, was shocked the first time I told someone "Wait your turn, we'll get to you."