Most versatile cartridge?
HP 951.
It is the most common variant of ink cartridges on the market, and prints up to 700 pages!
Oh, you mean boom-boom, bang-bang type stuff...
I'm with Scorch.
.44 Mag all the way.
.45 Colt sounds great, but it's limited by weak original frames and questionable imports. Good in modern (domestic) frames, but not reliable in other stuff.
.357 Mag is just too offensive to most shooters.
Weak stuff is okay, but "full-house" loads are too much for most shooters. No good.
Then again, there's always a wrench to throw into the works...
.480 Ruger.
No one that has fired mine has complained.
Last June, my petite, light-weight, recoil-shy niece fired my .480 Ruger for the first time.
7.5" Ruger Super Redhawk.
Full power 375 gr WFN handloads.
She doesn't even like .38 Special.
Response: "Ooooh. How much ammo did you bring? Can I do that again?"....