Here are my details:
Derivative applicant to my husband's application. He got his GC in May while I was transferred to the Baltimore office for interview in April because of FP issues. Through mixup at INS, I didn't get interviewed till 9/10.
I brought all the original documents supporting the papers filed with the I-485 (marriage certificate, birth certificates for both of us, passport(s) including expired ones from when I first entered the US, etc.) Now note that we had a "twist" in our situation--last August, 3 months after he got his GC, my husband had switched employers. I had two letters with me---one from his former employer confirming his dates of employment and another from his current one. I also had his last 6 paystubs from the old employer and the current one from the new one.
As it happens, the only things my interviewer asked to see were the marriage certificate and my birth certificate and passports. Only at the very end did he casually ask if my husband was still with the original employer and I honestly answered that he very recently changed. The IIO just shrugged and said "Okay" and didn't ask to see anything on paper.
I did not get my PP stamp because I needed to get police clearance due to my FP problems. But the IIO told me that was the only reason why he is not stamping the PP.
I am still waiting at this point.
Of course the documents that are "required" kind of varies from interviewer to interviewer. But I think it would be safe to bring all original documentation supporting papers filed with I-485 and employment paperwork (I am assuming your primary, like mine, is an employment-based application).