if you are looking at non-"custom" options, I don't think you can beat the Galco D.A.O. holster. high quality, great design. protects the gun well, and you can adjust the tension on the gun with a screw. I think it's outstanding, I've got one stamped with the ruger logo for my Blackhawk.
the Bianchi 5BH or BHL is another non-custom option that is very good.
for custom options, I have holsters from Simply Rugged and El Paso Saddelry which are great. I'd give the nod to SR if you want a pancake style, EPS is you want a regular threepersons style.