Marc Daniel Nelson pulls a favorite trick from Ken Caillat's book on making Fleetwood Mac's Rumours: varispeed guitar recording, used heavily on Lindsey Buckingham's tracks.
Slow the tape machine or digital clock down, learn and tune the guitar part at that slowed speed, then bring it back to normal. The pitch jumps up, similar to a high strung or extra 12 string layer.
It works best on arpeggiated or fingerpicked parts with a circulating feel. Layered above a normally tracked guitar, it adds an ethereal, sprinkled top end.
The real payoff is glue. Once the normal guitar sits under this raised, airier layer, the two blend into something that feels bigger and more magical than either part alone.