We brought everything we submitted to USCIS, everything we submitted to NVC, all the papers that we mentioned in our review, plus additional boarding passes/pictures/call logs from things that happened after we sent papers to USCIS.
They asked for NOTHING, except the required papers (which we wrote in the review), but some people do get asked for more. Most people go in with a huge stack of papers. It's better to be over-prepared!