Championship, CD/RN (preferably both), CGC
I understand the concept of performance titles other than Schutzhund as there are many venues out there in which a dog can compete, such as Ringsport, Agility, Herding, Obedience, etc. Personally, I would like to see something more than a CD or RN - I'd like to see the handler going further with their dog before breeding.
Nothing against earning a CD or an RN, but IMHO those are steps toward further titles, not the end-all, be-all a dog should have for breeding. IMHO it's like breeding a Schutzhund dog that has earned nothing but a BH in the sport.
A CGC should be a given for any dog with basic obedience, and I wouldn't really count it. I see a lot of backyard breeders who boast on their websites that their dogs have CGC titles, as if they're some big training achievement. (I guess to the average Joe who does not do any training with their dog, it could seem that way, however.)
Health testing, such as CERF and OFA should be a given for anyone who is going to breed. I am surprised that a lot of people mentioned those in this thread, since those aren't titles and the topic for the thread is which titles a dog should have earned.