If you are going to vatican you should take the tour of the necropolis below the vatican.
Here is a link for some basic information on it. I don't recall the exact price but it was around $10 dollars per person and is totally worth it. By doing this you go through a different gate and skip the 2 hour line to get into the vatican the tour lets out inside the vatican.
you have to sign up for this in advance. i think i sent an email saying when i was going to be in rome with the number of people who would attend and they sent me a response a couple of weeks later with the dates. they only let 12 people per tour.