What's your favorite heirloom bean? About to order from Rancho Gordo and

Royal Coronas, Scarlett runner, Eye of the Goat. Any Rancho Gordo bean is very good, try them all.

I second the Marcella praise. I also love their borlottis. I just got the Rancho Gordo French Bean recipes book and I quite like it.

I'll jump on the stilllifewithwhisk bandwagon and recommend the Good Mother Stallards. They're incredible when prepared simply and the broth they produce is so good that I find myself drinking it by the ladleful.

If they're available, Royal Coronas are special and worth getting your hands on if you haven't tried them yet. They're absolutely enormous and so creamy and buttery. I also love the delicate Marcellas, the hearty yet subtle Rio Zapes (these also develop a delicious pot liquor!), and the Santa Maria Pinquitos. While easy to dismiss, the Cranberry, Pinto, and Midnight Black beans are also very good. Truth is, I haven't met a RG been that I didn't like. I've tried most of the varieties currently available and they've always been a delight.

If you need to round out your order, I'd also recommend the black lentils and spelt, if they have it.

I don't know if they stock a bean called Cargamento, but they're definitely worth a try if they do. I've never seen them dried, but have been using them canned by Goya for busy nights. If I could find them dried, I would get them. They are plumper, rounder and more succulent than the more usual varieties like pinto, black beans or kidney. Worth seeking out.

Haven't tried them all, but especially liked their Cranberry, Cassoulet (Tarbais) and Large White Lima Beans.
Also liked the ones stilllifewithwhisk mentioned.

Good Mother Stallard and Christmas Lima beans.