I've always thought it would be fun to compile a list of famous rejected research papers, ones that later turned out to be highly influential.
For example, in My Life as a Quant, the author tells the story of how the famous Black-Scholes paper (which describes how options should be priced) was rejected several times. The work eventually led to a Nobel Prize in economics. (Yes, I know, there technically is no Nobel Prize in economics).
Then there's George Akerlof's work on asymmetric information. I don't recall exactly, but I think the reviewers thought it was too simplistic. It also led to a Nobel Prize in econ.
And then there's Tim Berners-Lee's original paper on the World Wide Web. He describes his experiences in his book Weaving the Web. I think it was submitted to a hypertext conference, but was accepted only as a demo. I'm guessing reviewers didn't see much novelty in the work, which probably was correct from a research perspective.