I bought the ID Anthology, which has fully registered 'legal' copies of every game published by ID. Up to Quake 1, which was the current game when the Anthology was published. There is more than the CDs in the box, there's also a Long Distance Dialing time card, some sort of pewter swag item, and there was a T-Shirt but I am certain I wore that out.
I have a lot of Walnet Creek CDs, too,
I also have a CD called the 'C CD' published by a company called Alde which was purportedly a C Source Code CD (it has a collection of public domain source code on it) but is really a hidden stash of girlie GIFs. The hidden directories are simply 'hidden' with the 'hiden' filesystem flag. It's also ISO-9660 non-compliant, I am not sure how, but it kicks out certain errors. I suspect it's either pre-ISO-9660 or was just from the era before the standard was strongly in place (or the publisher was sneaking out a CD of girlie GIFS and not paying much attention)
I hope someone is archiving the old CDROM porn collections. There were a number of publishers, and it was cheesy but quite expensive for the time.