Do you mean the E34, E39 or E60 M5? Only reason why I ask is that I have an E39 M5 (Imola Red/Caramel), that your more than welcome to have a drive of if you've not driven one before?
As for my list....
1) Aerial Atom 2-300
... love that photo... instant facelift
2) Ascari KZ1
3) BMW X5 3.0 Diesel
atom: super sounding, light as buggery, makes it the ultimate track toy... even Jeremy Clarkson liked it...
ascari: ... has people saying.. its a what????.... and it has the same S62 that my car has.. 1:20 around the TG test track (10th fastest) is nothing to sneeze at.
X5: Great for lugging prams, and all manner of child related paraphanalia.