I have a few different favorites:
If I want to make cows, I would have to say that Rambo 502 is the bull that did the most for the entire breed. He had some problems too, but nearly all were great producers.
I have a bull called Rattler 908. His sons are by far the easiest I have raised to look at and the commercial ranchers absolutley love his sons. They are extremely thick, long, excellent performance, and good enough carcasses. He also had the best set of feet and legs on a Red Angus bull that I have ever seen. His daughter are pretty good heavey milking cows, but the EPDs say different. He only has a 4 for milk.
Dakota Copper 29K - Don't own or never have used. But I did buy a son this year. His daughters have the ideal amount of capacity and some of the most beautiful udders in the breed. His sons are very powerful thick bulls too.
I only used Grand Canyon 1 year and sold most of the cows bred to him so I never got a good use of him, but his daughters sure seem very good, easy keeping, and excellent udder and leg structure.
121R is the bull that will bring muscle and bone back to the breed. After all the Cherokee was used, we loss alot of performance, and I think this is the bull that will bring it back. He is extremely thick rear quartered and has alot of performance with big REAs. But he isn't the kind of bull that will work on every cow. You need to be careful how you mate him.
My least favorite bull is Cher. Canyon. I saw him as an 18 month old bull and was one of the pooest looking bulls I have seen. Now his offspring have poorer feet, udder structure isn't good, and I have herd the calving problems too. I will always try to stay away from this pedigree.