"What do you want to play?" Bono said to him. "Get a guitar for this dude. Gents, we have a surprise guest." The man said he was really nervous but once handed Bono's acoustic guitar he began playing "All I Want Is You."
It started with just Bono on vocals, but soon enough the entire band joined in for a moment the man is unlikely to ever forget. When it was all done, Bono gave him the guitar.
Source.
This is so amazing.
