Elvis Presley, Frank Sinatra, Nat King Cole, the Mamas and the Papas, Dean Martin, Jan & Dean, the Righteous Brothers and Ray Charles to name only a few.
In 1965 he had significant studio work with Phil Specter as well as with the Beach Boys so much so that he toured with them. Campbell estimated he was earning about $100,000 per year for his studio work in the mid-1960s.
He played on the First Editions psych-drenched ‘What Condition My Condition Was In’ and the 12 string intro to The Beach Boys classic ‘Dance Dance Dance’, and he is playing on Sinatra's ‘Strangers In The Night’
Get a load of Glen Campbell’s guitar skills when he played the WILLIAM TELL OVERTURE in a concert just 2 years ago:
http://www.youtube.com/watch?v=uf8ONq1Dtrg