Last week David Bowie showed up for the encore of a David Gilmour show at the Royal Albert Hall, and helped out with the vocals on "Comfortably Numb."
The thought of hearing Bowie's voice singing "Hello... is there anybody in there? Just nod if you can hear me..." makes me weak. I think if I'd been there I might have passed out.
Update: yes. Oh, yes, oh, yes.
P. S. I am very amused to note that mentioning my nipples on Fark resulted in a whole bunch of hits on this site yesterday and today.