There probably are other artists who use this effect, but I'm most familiar with it through The Edge's playing. He uses this "shimmer" effect on a lot of songs. Probably the most well known example is "With or Without You". If you listen to some live versions, you can hear it very prominently starting in the second verse. A similar (if not identical) effect is on the album version, though. He uses this same effect in other songs, too. Sometimes the use is more subtle than others.
Shimmer can easily be mistaken for a keyboard. It's so smooth and lush sounding, you'd swear there was no way a guitar was producing the sound. But, it really is an octave up effect combined with delay and reverb. Check out any of the "Crystal" presets ("Crystal Echoes", etc.) on many Eventide units. It pretty much nails the "shimmer" sound.
Jeff
