This really depends on who is on the team. Believe it or not, most residents and attendings can pick up on the fact that the person is a gunner and is annoying. Unfortunately, sometimes this is not the case.
Discuss this with your senior resident, call him/her aside and say, "hey look, I am really trying, but its hard to do when so and so won't give me chance to answer pimp questions, yada yada yada". I think that is the best approach. I was in a situation like this once, the gunner on my team would pimp me in front of rounds, pimp the team intern, finish answers to questions before you even had a chance to think, etc. etc. When the senior resident met with me in the middle of the rotation to discuss my performance and if I had any complaints, I really wish I had brought this up to him. Oh well, my mistake, don't do that same.