To answer the question, the gun I have on me at the time.
I consolidated my calibers in the 90's. My stocking calibers are: 22LR, 9MM, 357 Mag, 5.56 a recent addition, 7.62x39, 308, 12 gauge, 20 gauge. I have a few other calibers for sentimental reasons, but I don't stock major ammo for them.
Besides consolidating calibers, I did my best to consolidate magazines. Example: all but 1 of my 9MM take the Glock magazine, that includes my 9MM carbines, even my Marlin Camp.
This consolidation has got my through every "panic" from 9/11 to present day. Remember, you can't have too many magazines or ammo.