In the US I've found most clinics are actually fairly picky about the traits they will accept in egg "donors"--who are usually reasonably well-compensated, which is, I suppose, why they can be so selective.
(I think it might be nice to pass on my genetic material. But no one paying through the nose--or any other orifice--for genetic material wants mine. Can't say I blame them.)
(Why anonymous? Because I have a relationship and I prefer not to write about it in "public".)
Intelligence. (Ideally, someone slightly smarter than I am.)
Sense of humor--by which I mean someone who holds nothing too sacred to joke about, and who also appreciates terrible puns. And It's not enough to simply appreciate humor; they have to be able to crack a good joke themselves.
Kindness--I dated someone who was sweet to me but otherwise generally abrasive and obnoxious once. Never again.
Rationality--no, I don't care if they've read the Sequences. I do care if they're willing to engage in argument fairly, change their mind when appropriate, evaluate evidence rationally.
Emotional stability--I can't deal with the stress of dating someone emotionally fragile or overdramatic.
Sexual compatibility.
As for physical traits, most people are physically attractive to me once I've gotten to know them and found their mind attractive first. I have some preferences but I can't think of one that is a dealbreaker. But they do have to be physically attracted to me also.
Companion and lover. Someone I can escape from the rest of the world with, can trust to care about me and want to help me, can enjoy life experiences with. Also someone I respect and admire, whose life I want to share in.
Ideally, we would live together, but be able to tolerate extended separation without getting upset. I like to be alone frequently, and to spend time with friends (even the friends my partner doesn't care for); I also travel for events and various opportunities. But it's very nice to have someone to come home to, to share most days with.
We should have at least some similar tastes, or it's not enjoyable to share things we like. In particular, someone I date has to be at least tolerant of my musical choices, because I want to have music playing frequently. At the very least, they should not be dismissive or disdainful of the things I like.
Reasonably so. I don't hold extreme views on many things--particularly ones that are very complex. The ones that I do hold extreme views on are very important to me. I have to be able to respect my partner; I can't respect someone who holds many strong views that I believe to be unethical.
Being seriously religious. Physical or emotional abuse. Excessive jealousy. Lack of respect for me. Anti-intellectualism.
(Also, I've never dated anyone who could not write both music and code, but I don't think this is necessarily essential.)