I don't disagree, but I want to elaborate on some of these suggestions. The only must have books for actual Step1 studying are First Aid and RR Path (Goljan). When it comes down to the nose-to-the-grind Step1 studying, there's just not enough time for many resources. The others are important however, but I would classify them as must have books if you want to rock your courses (which is indirectly studying for Step1). For each system in path, read the Goljan chapters and do the Robbins and Webpath questions. If you're a textbook guy (like me), big Robbins is awesome. It's actually one of the only books I plan on keeping. It really helps out if you want more detail, if your teachers didn't do a very good of explaining a topic, or if they didn't explain it at all.
For Micro, CMMRS is money.
I used BRS Phys and BRS Phys Cases during my first year physiology course, but I don't think I picked them up more than twice during step1 studying and that was just for a few topics. Other people on here swear by these books though.
In my opinion though, you can't do enough questions. If I could do it all over again, I would try to get through all three of the big question banks (UWorld, Kaplan, and Rx). Each bank has a slightly different style of asking the question, and as Goljan says in one of his lectures, there's only so many ways they can ask the questions. So, just by the laws of probability, if you do 8000 questions in preparation, most of the questions on the real thing will be similar to a question you've already had. Just my opinion though.
Good luck!