I'll take my 45 Super if ammo isn't a problem. I also see you didn't list the 357 & 44 mag. These can be had in the Desert Eagle, same as the 50AE.
The 45 Super, for those umfamiliar with this round throws 45 caliber bullets faster than 357mag velocities. All from a 39 oz 1911A1!
The 9mm can be used in tiny little spitwads (okay, a Keltec P11 isn't as tiny as a P32) to carbines and machine guns (UZI's, etc.)
<sarcasm on>
You he-men should figure out how to get a .50 BMG autoloader in a handgun package. Saw off the barrel to about 2 inches, put on a pistol grip, etc.
<sarcasm off>
My 4 1/2 inch high standard HD Military .22lr would be the one I would keep. For target shooting, plinking, small game hunting and shootability it is tops in my book. I would use it in self defense if I had to, but I'd prefer a shotgun or a revolver.
500 rounds for 10 bucks doesn't hurt either. Good shooting, Weagle