What guitar is Peter Buck playing in the video clip for the song "What's the Frequency, Kenneth?

The powder blue guitar was a gift to R.E.M.'s Peter Buck from Courtney Love. The guitar had previously belonged to her husband, Kurt Cobain. In the video Buck plays the guitar upside down in tribute to Cobain.

http://remprojectblog.blogspot.com/2014/02/monster-whats-frequency-kenneth.html

The guitar is called a "Jag-Stang", because Cobain invented it by blending two Fender models together (i.e., Jaguar and Mustang). After Cobain's demise Fender began commercially producing "Jag-Stangs".

http://www.rollingstone.com/music/pictures/20-iconic-guitars-20120523/kurt-cobains-jag-stang-0882295