I know that many of us could post a list of hundreds, but let's keep this to three please.
I wouldn't say these are my ultimate favorites, but they are in the top 10.
1. Paul McCartney, almost anything on Sgt. Pepper
2. Nathan East on Eric Clapton's 24 Nights. He takes those wonderful licks of Carl Radle and Jack Bruce and updates them, brings something new to them.
3. Dee Murray. His work on Elton's best albums really adds to those songs. A stellar performance is on Funeral for a Friend / Love Lies Bleeding