I went to Rome and most useful thing i brought with me was an audio tour from www.variantguide.com Lots of useful information inside and really comfortable to use if you used to walk around a lot.
If you like to walk around and enjoy atmosphere of Rome, personal audio tour is the best thing to buy before you go to Rome. This particular tour had almost all the places I wanted to see in Rome, they even had an ancient Flower market in the middle of Rome, very special place. Audio tour gives you lots of advantages: you don't have to be in the middle of noisy crowd, you don't have to wait anybody in your group, you don't have to like your guide, you don't have to do all the tour just becouse you paid to him and when you change your mind you still have to follow him, or if you want to have a quiet break and have some coffee, you are absolutely free to do it and only then continue your tour.
Favourite spots:
Arch of Constantine, Campo di Fiori, Colliseum, Catacombs, St.Peter's cathedral
What's really great:
The best thing was to observe ordinary people and their life, passing through while you just seat, enjoy your coffee and watch it as real time movie! Beautiful city with beautiful people living in it.
Sights:
Il Campo dei Fiori, Fountain of the Niads, catacombs
I personally would not like to use an audio tour because I feel that it would shut my off from the real world. But I suppose some tourists would like it. Could you expand this report and show us where you went and what you saw?