yes those gunners can be rough, but I do agree with the other about not listening to them pimp each other before a test, that is one way to freak you out.
Gunners will be gunners, just remember why you are there, what goals you want to accomplish, etc. If you are happy with your performance and meet your goals, then screw the gunners. That simple. One of the biggest problem with medical school is that everybody is pretty intelligent, I mean even the quote unquote dumbest person in your class is smarter than the average joe, so egos will collide in that environment.
There is no way to put gunners in their place, some are very rude, I had one person in my class I couldn't stand to even listen to her speak, she was the class expert on everything and ironically had a minor in everything that we were taking at the time, neuro, psych, etc. Whatever! Who cares!
If you get what you want in the end, the residency you want, the specialty to want, and acheive your goals, then gunners don't matter.