I saw a solo tuba concert once that was pretty amazing. There is apparently music out there written for the tuba.

 

In a rock setting another guy who should get a look in is the new Metallica bassist Rob Trujillo, not for his work with Metallica (it has only been live so far) but more for his work with Infectious Grooves and Suicidal Tendencies. He has also played with Ozzy Osbourne. Rob Trujillo does an amazing slap/pop cover of Led Zeppelin's The Immigrant Song, well worth checking out if you can find it.

Rock guitarists there is possibly too many to list as fantastic instrumentalists.

Rock drummers I would add Danny Carey(Tool), Raymond Heherra(Fear Factory), Josh Freese(almost everyone laterly APC), Mike Portnoy, Neal Peart and John Bonham.

In modern rock piano/keyboards I would say Billy Joel is amazing. Saw him in concert with Elton John and Billy blew him from the stage, far better technically and on a par for soul. The difference between self taught and classical training was apparant, as the classicist blew the self taught away.

Vocalists I would not call instrumentalists but as they have been brought up here goes. Art Garfunkel (Simon and Garfunkel) had an amazing range and crystal clear voice. Bridge Over Troubled Waters is the classic S&G song. Chester Bennington (Linkin Park) will surprise some people here as being on a list of great vocalists, but anyone who can switch from the chorus of Crawling (full blown screams) tot he verse of numb (actually singing) in a concert without his voice noticably failing has some good technique. Others I rate (rock/metal) are James Hetfield (Metallica), David Draiman (Disturbed), Burton C Bell (Fear Factory), Freddie Mercury (Queen).

 

I love "The Immigrant Song"...