I've even had a some "gunners" in my undergrad classes. It is one thing to be interested and involved in a class, but it is another to feel like you need to share your 2 cents about everything that is brought up. These people also like to just "make sure that they understand" what is being taught (hence they restate everything that the professor just spent 30 minutes explaining and then come up with some random example that would try and counter it). I can only imagine that gunners become more annoying in law school, since they want to try and separate themselves from the rest of the class. Blah. The only separation that occurs is that the professor begins ignoring them and everyone else rolls their eyes when they raise their hands.
Is checking to see that you understood what was taught by paraphrasing the professor generally frowned upon, or only when it's obvious that you're doing so to self-aggrandize? When I'm not sure I understand what someone is saying in casual conversation, I have a habit of paraphrasing it and asking them if my understanding is correct. I don't want this habit to rub off on classmates the wrong way.