"I'm not getting anything out of this class." It's not our job to edutain you. Frankly, I could put a twelve course gourmet meal in front of you, but unless you pick up the fork and try the dishes, you're not going to get anything out of that, either. I usually only hear this when grades are close to coming out--a thinly veiled attempt at passing the blame off on the professor. Besides, a prof could be dry as dirt, but that doesn't matter--because you're not paying to be entertained. You're paying for access to someone else's expertise. If you're not getting anything out of it, that's probably because you mistook the clicker question for a remote control.
"I don't see why I have to take this class." The answer lies in the statement, sweet snowflake. Seriously, the fact that you can't figure it out probably means you desperately need to take it. The thing about a liberal arts education is that it's supposed to make you a more intelligent and engaged citizen who happens to have a speciality in a particular field. If you misunderstood that a university was supposed to inform you about history, science and the context of the culture in which you find yourself, you should've probably applied to a trade school. One of my favorite former student came to my office, no less, to bitch about his Spring schedule. After a few rounds of this particular argument, I finally choke-slammed it by asking, "So, please explain to me why you don't want to be a better and more broadly informed person?" Honestly.
"I have to get an A in this class." I would like to stab this excuse with a rusty spoon and watch it slowly die of tetanus. Actually, what I would really like is a snazzy comeback that incorporates all of the arrogant ballsiness and responsibility-evading of the student version. Sort of the academic equivalent of "Well, I'd like a gold plated toilet seat..." or "Let's wish in one hand and shit in the other, and see which one fills up faster." I'm open to suggestions.