1. Brooke Skye (05-09) - I think she only shot 1 b/g scene, which was actually a b/g/g, and it was a not great quality scene for In The VIP...
2. ...and Raven Riley (06-09) - I liked her but hated the quality of most of the content she made. I would've loved to see what she accomplished if she had actually bothered shooting for actual production companies that knew how to make good porn
3. Belle Knox (13-17) - shot a fair amount of content but, afaik, became one of "The Regretful" and dipped out of the industry completely
4. not a specific single performer but, in a general sense, there were a lot of girls who appeared in RKs Money Talks productions back in the early 2010s that I thought were knock outs but most seem to have done only that and nothing else. I felt like a lot of these scenes actually captured that "reality show, we'll pay this random chick to fuck" vibe and a lot of it may have been because JMac was such a god tier performer for both fucking and talking.
I found some really obscure forum thread once that ID'd several of the girls from that period because I was down bad to find one in particular (Sydney/Sidney Thomas from Money Talks "Real Reservations" 04/27/10) but even that didn't have info for most of them. They were one and done's. :(
I'm sure there are more that I only have one or two videos saved of or that I've seen once and forgotten about but those are some of the ones that really jump to mind.