Brooks, Cal, Frank, Jim, Earl, Eddie.
There are a handful of O's that are going to be first on the list, and rightfully so. Below that list is a bunch of other guys who drift in and out of the public consciousness.
I can't put a finger on why, but I've always thought that the name of Mike Cuellar doesn't have the as much cache as it should among O's fans. Is it because he spent time with so many other teams? Is it because he was Cuban during the Cold War? I don't really know.
I wasn't really a big baseball fan when he was at the height of his game, mostly because I wasn't alive yet, but reading through his achievements you'd think he would be a legend.
He was the first Latin American born pitcher to win the Cy Young award in 1969. In 1970, he led the league in wins and complete games. He was a part of one of the most dominant rotations ever seen from 1968-1971, which included 3 consecutive AL Pennants and 1 World Series. In game 3 of the 1973 ALCS he pitched 11 innings. The O's lost 2-1, but if there was ever a hard-luck loss, that has to be it.
The 1971 staff of Cuellar, Palmer, McNally and Dobson was one of only 2 rotations in history with four 20 game winners. That's amazing. He also once recorded 4 strikeouts in one inning, and I don't want to know the odds on that one.
I'm not suggesting by any means that Cuellar is an unknown, but he definitely should be more known.