Cross of Thorns - Black Sabbath (
Cross Purposes)
I could name 50 Sabbath songs that would fit this bill but I'll stick to one
You Keep On Moving - Deep Purple (
Come Taste the Band)
I Looked Away - Derek and the Dominos (
Layla and other Assorted Love Songs)
This might not fit the bill, but of all the Clapton songs I've heard be talked about this one comes up rarely.
Temple of the King - Rainbow (
Ritchie Blackmore's Rainbow)
My Fathers Eyes - Eric Clapton (
Pilgrim)
Lonely Days, Lonely Nights - Whitesnake (
Come An' Get It)
Passion Play - Jethro Tull (
Passion Play)
Is While My Guitar Gently Weeps by the Beatles one of their more obscure ones? It isn't one of their most famous ones but I'd be shocked if it was obscure considering the quality and the fact that Clapton plays on it.