Supergroup

[cartman99]

Lead guitar
Bass guitar
Drums
Keyboards
Vocals

You can have who you like, who you having?

[Dr Wu]

You could probably just pick Prince and the little so and so would be able to handle all these better than most.

Wouldn't surprise me if he could do them simultaneously too!

[Dusty Bin]

LG : Joe Walsh
BG : Mark King
D : Cozy Powell
K : Steve Winwood
V : Roy Orbison

[Whickerman]

Lead - Joe Satriani/Brian May
Bass - John Entwhistle (The Who)
Drums - Keith Moon
Keyboards - Rick Wakeman
Vocals - Rod the mod.

Course, when all this has been tried in the past it's failed miserably (though not commercially). See the Travelling Wilburys, where instead of bringing the best of everyone out, it seemed to just settle at the lowest common denominator for the band. Sad really.

[cyanide]

Lead Guitar- Michael Angelo Batio
Bass Guitar- Steve Harris
Drums- Dave Mackintosh (Dragonforce)
Keyboards- Vadim Pruzhanhov (Dragonforce)
Vocals- Tim "The Ripper" Owens (Iced Earth/Judas Priest)

[steviebnw]

Slash
Flea
Dave Grohl
Elton John
Robert Plant

[Merlin77]

Jimi Hendrix
John Entwistle
Rick Allen (Def Leppard)
Ray Manzurik (The Doors)
A young Rod Stewart

[Kidd72]

Lead guitar: Vinnie Moore
Bass guitar: Mark King
Drums: Cozy Powell
Keyboards: Beethoven
Vocals: Freddie Mercury

[Steve_ref]

LG - Eric Clapton
BG - John Deacon
Drums - Keith Moon
Keyboards - Keith Emerson or Rick Wakeman
Vocals - Karen Carpenter

How about a 5 piece group where each member must be one from a seperate decade.
Mine -
LG - Clapton (I know a bit of a cheat considering he started with the Yardbirds in the 60's) (80's)
BG - Jack Bruce (60's)
Drums - Mick Fleetwood (70's)
Keyboards - Marc Cohn (90's)
Vocals - Joss Stone (00's) or Connie Francis (50's)