For the horrific one gun choice in a world gone topsy turvy - for car/home/personal protection - and solely for it's wide ammo range - I'd likely keep my, gasp, Governor!
For the 20k+ rounds of fun .22 rimfire I have, and accepting it's stopping potential, I'd consider my fun plinker - my 3" 63.
Accepting that it will be difficult - even on someone volumetrically challenged as I am - to CC - my 4" 64-8 is a fun plinker with my supply of .38 125gr JHP homebrews and sufficient protector commercially made +P 158gr LHPSWC ammo, both of which are essentially coincident POA/POI hitters from 5-20yd with it's fixed sights.
If it's purely nostalgic considerations, my first-ever S&W - a 625-7 MG in .45 Colt my wife shocked me with - along with my stash of homebrew ammo - would get the nod.
If it was a house fire/tornado/attack, I could quickly grab a 'bug out bag' with copies of house/personal documents, knife, water purification, flashlight & batteries, and a 2 5/8" PC627 UDR with +P 158gr LHPSWC on moonclips. That is a delightful revolver - fun, too!
That Governor became a real choice after perusing several big discount stores for ammo - no .22/.32/.380/.38/.357/.44 anything. All had .40 - no help here - and .45 ACP & Colt!
Happy New Year!
Stainz