Open Carry pistol
something big, scary and impressive like a HK USP, Glock 17, SIG P226, 1911, Walther P99, etc for open carry usage for all to see. I'll take the USP in .45acp!
Concealed Carry pistol
a small but powerful ccw gun for concealment, like maybe a SIG P245 or P239, Colt Officers, micro Glock, Kahr, etc. Gimme the P239 in .357 SIG!
Hideout pistol
ultralight .38 special/.380 small hideout gun like a Ti or Sc Smith & Wesson Jframe, Taurus titanium, old S&W or Colt aluminum frame revolver, Colt Pony or other small .380, etc. I'll take that S&W 360 in .357mag!
Target/Plinking pistol
something really really accurate and (preferably) cheap to shoot too. For target use to keep your eye sharp, and plinking just for fun too... A quality target grade .22LR, somethig like a Browning Buck Mark, Ruger MkII, SIG Trailside, etc. Gimme the Trailside!
Thats pretty much my "minumum"...
On top of that, and given some more funds and other sitiuations I'd add:
Woods/hunting sidearm
something to carry as a sidearm when walking/hiking/hunting with a long gun. There for emergency use and maybe mercy shots or possibly some small game up close under the right conditions. A 4 inch double action .38/.357/.44/.45 revolver pops to mind here, but a short barreled Colt SAA would do nicely too. An older S&W Mountain Gun or one of the new ultralight Lframes might do nicely, as would a S&W 625 in .45acp (albeit kinda heavy). Colt Diamondback/Python is heavy too, but would be nice as well. If S&W ever made a Sc "M325" in .45acp I'd probably take that, until then I'll have to stick with the "heavy" version, the 625.
Hunting pistol (smallgame)
A 4 to 6 inch .357 would be nice here, as would that 625 in .45acp/ar or even a lightweight 4" .41/.44/.45colt with light loadings, again, something like a S&W mountain gun would be nice. A decent .22LR revolver or autoloader will fill in here nicely for the really small stuff, and if you pick your big game hunting pistol well then they will balance each other nicely and leave no gaps in your hunting capabilities. My favorite is the 625 here too, it serves double duty I guess.
Hunting pistol (big game)
Something like a 6" to 8 3/8" .41 or .44 mag, or maybe a stout old Ruger in .45 Colt with some hotter loads. A T-C Contender in .35 Rem/.45-70 or one of the powerful wildcat calibers would be nice too. I'll take the T-C Contender with 2 barrels, a 12" hunter in .223, and a 12" hunter in .45-70. That would be a pretty useful combination.
On top of these I might add a few "competition" pistols, like a revolver or single shot pistol in a high velocity caliber for Silhouette shooting, and maybe a couple of accurized Bullseye guns in .22lr and .45acp.
I'd just order another barrel for my T-C here for the silhouette, maybe one in .357 Max or .30/30. And for the Bullseye shooting I'd go with a pair of 1911s, both homebuilt then sent out for tweaking, one a .22LR and the other a .45. Both setup as identically as possible.
Well, thats pretty much my "minimum"