Autoloaders: 9mm, .40, .45
Revolvers: .357, .44
Rifles: 5.56, 7.62
Shotguns: 12GA
I'm pretty consolidated in calibers, but when I look through my ammo stash, I'm not sure that it does any good. All my shotguns are 12GA, but I have 4 or 5 different types of 12GA rounds lying around. Don't get me started on the rifles. Each precision rifle takes a different load, even if it's the caliber.
So basically, I have a different ammo for each gun, so why bother having the same calibers?