Cool topic bensonp. It's funny, that Chet / Jerry was the first one to pop in my mind. There are many, many great guitar duets featuring Clapton plus anyone, but for this post, I'll offer some sappy songs that duets seem suited for.
First one not so sappy, but I always liked it. Carly & James doing Mockingbird live:
This one, my wife says is "our song" - this version, not Smokey's. The soundtrack was pretty new when we met and after a topdown cruise in my '67 mustang that evening it seems appropriate.
And this may be the best sappy duet of all time. Nat and Natalie Cole "Unforgettable"
Rule No. 1 - If it sounds good - it is good!