Cliff Burton, just to see the expression on his face once he would listen to Metallica's recorded output after his passing
on another note
if these dead rockers could be brought back, wouldn't it be way much more fun for them to form a massive band?
just imagine John Bonham and Keith Moon drumming while Cliff Burton pounds the bass, with Zappa, Hendrix, Dimebag and SRV trading licks, all the while Janis, Freddy Mercury and Jeff Buckley wail at their mics
and then a Harrison/Lennon unplugged jam with Jerry Garcia
at the end Elvis would show up, say "thank you, thank you very much" and Johnny Cash would snag the mic off him and say "get lost fat ass"