People who can't follow simple directions and/or requests.
Case in point: I went to Quiznos earlier after my workout and ordered my usual sandwich, and even though I only go there once or twice a month now (cause it is somewhat out of the way for me now), the manager still knows that I like it extra done, so he will run it through twice or slow it down (if it is slow and there is no one behind me). Anyway, he told the guy working how I like it, and what does the guy do? He slows it down, but then as he stands there on other side waiting for it, he peers in and then speeds up and grabs it as fast as he can, obviously so he can get it done and get back to playing on his phone. I rolled my eyes and didn't say a word. Then, he asks if I want anything else on it, and I specifically say, "Just a little bit of lettuce," and he proceeds to grab a big enough handful that it would fill a large salad bowl. Idiot.