Interesting category- I'm surprised there aren't more nominees. Again, I have a little research to do before I vote.
My nominee is the Big Man, Clarence Clemons. C is best known for his role in the E Street Band, and the sound of his horn is instantly recognizable. He was also Bruce's main onstage foil for many years, until his health declined and he couldn't move around as much.
His "Jungleland" solo is probably his most well-known, but I love many of his others, including "The Ties That Bind", "Sherry Darling", "Hearts of Stone", "Back in Your Arms" and "Drive All Night". He's sorely missed, and I miss his background vocals as well ("Santa Claus is Coming to Town" just isn't the same without his "Ho, ho, Ho!") Here's one of his best performances, "The Fever":
https://www.youtube.com/watch?v=p3ocPTveQkg
Clarence also played with other artists, including The Grateful Dead and Ringo Starr's Allstars, as well as having his own band, The Red Bank Rockers. The last recording he played on was Lady Gaga's "The Edge of Glory". He also dabbled in acting a bit.
Now, Bruce Springsteen on harmonica is an interesting choice. As much as I love to watch/ hear him play, I don't know if Bruce is really an accomplished enough player to be considered HOF caliber, much in the same way I'd never say he's in the same class as a guitarist as some of the greats, though I certainly love his playing (I'd be curious to hear the opinion of any harmonica aficionados). That said, I do really love what he did with "The River" on the Reunion Tour (also features gorgeous sax intro by CC):
https://www.youtube.com/watch?v=wU_WZdUqQY4