I took with me everything I could think of: Birth certificates, marriage certificate, Bank statements, even family photos, job offer letter, company's annual report, pay stub, mortgage statement, passports, etc.
The officer took it all but she only seem interested in the following:
1. Proof that the job was still being offered (job letter), and
2. Proof that we had always remained in legal status while staying in the US (Immigration forms, I-94s, etc.)
In my case, there was some confusion with regards to how long had I been working in the company and the date of my first entry.
Interview took place 6/16, we received our GCs in the mail yesterday 7/6.
Good luck.