Choose any two musicians and/or bands to play together, they can be alive or dead, to make an album together.
Mozart and Jimi Hendrix-> Before he died Hendrix said he wanted to do some rock/classical mixing. I think it'd be brilliant to see the best of each genre (my opinion) make something together. Even if their personalities might clash xD
the Black Keys and Jimi Hendrix-> My three favorite rockers make something together would be great.
Animal Collective and the Beatles-> Both have bizarre lyrics and really weird good music vibes. Would be cool to see what they came up with together.
You get the idea. Feel free to state reasoning behind your choices.