I narrowed things down to 9mm, .45 ACP, 7.62x39, and 7.62x54R.
Of course, this doesn't factor in my .38 and .357 revolvers that I use for CCW and automobile carry, respectively.
I further complicated the whole consolidation thing when I recently picked up a Mossberg 590A1 12 gauge. It's going to be hungry for ammo, too.
Oops.
I'm actually going the other way. I found a source for 357 SIG ammo and bought a conversion barrel for my 40 S&W. I figure the more different calibers I have, the better the odds of finding ammo.