I relinquished first authorship of a paper.
I worked on this paper all through my time at JPL and Caltech. It was my project, my experiment and I've been hanging onto it, trying to push revisions through on my occasional trips to the States over the past two years. Thanks to the work done by my former graduate student, it really is nearly done now. He'll have to write up the supplemental experiments that he did, but the core content of the paper won't need to be changed.
I don't think anyone would dispute my claims to ownership of the paper, despite the additional work he did and the data he re-took. I also don't think many people would have agreed to have their names demoted from the coveted position on a paper. I'm not claiming sainthood for having sacrificed it or anything. It would be untrue if I were to claim that I didn't have a great deal of ego invested in the work. However, he needs authorship on this paper a lot more than I do. He's beginning his fourth year, the work he did carrying on my project has consumed most of his graduate career and he wants to finish his Ph.D. next year. He'll get another publication out of a separate study, I'm sure, but it might not be submitted until after he defends his dissertation. I'm switching fields and I'm unlikely ever to become an academic in experimental chemical physics. I don't desperately need to be first author on this paper, although it'd be nice if it finally got published so I'd have something to show for my post-doc. I know I'm doing this for good reasons.
I'm still finding it difficult to let go.