If I could only have three:

HD and around the farm: .40 or .45. Sig P229 is my first choice, S&W M&P .45 is second.

CCW is a G26.

Third would have to be a "convenient" pistol, such as a J-frame airweight S&W revolver for easy concealment around the house, yard, etc.

If I can only have three, I don't need a range gun. That's a luxury.

Two Glock 17s and a Smith J-frame .38.

HD: P220R .45ACP
Carry: P229 .40S&W
Range: P226 9mm

Only Three? Thats easy

Home Defense: SIG Sauer 556
Every Day Carry: SIG P220 BR3 SAO
Range Pistol: SIG P210 (9mm)

Now what about Anti Zombie Rifles?

In an ideal world:

HD: HK45 w/ TLR-2
CC: Either HK45c or SW 340SCPD
Range: Les Baer 1911

226 9mm
220ST 45
Ruger RH 4" 44mag

HD: Ruger GP100 .357

CC: Sig 229 .40 cal

Range: 226 X-Five .40 cal

Well, you kind of did not rule out a backup, well you did, but I don't ;-):

Home Defense: Sig P-226R 9mm with X300 light, Glock 30 in the Gun Guard as backup (and an 870 Rem. around the corner if needed).

Concealed: Sig P-229 SAS Gen II .357 Sig, S&W 342 (.38 +P backup)

Range: Wilson Combat Supergrade, .45. No need for backup, see above.

T.

HD, CCW, Range: Beretta 93R auto

A bit more kick: AMT .44 Automag or Wildey .475 Magnum

Heavy duty: Sig 556 Pistol

Glock 19 for CCW
Glock 21SF for HD
High Quality 1911 for Range use

My 3

1911 full size.
P220 elite
p226 w. german.

oh crap, I already have those 3.

Hmmmmmmmm?
HK45
P7M8
1911

But I carry a J frame everyday. So again I say Hmmmmmmm

Lets see...

P226ST .357sig
H&K45C
X5 9mm

Home Defense: HK USPc Combat (.40)
Concealed/Every Day Carry: HK P2000SK (9mm)
Range Pistol: SIG Sauer X5 Tactical

I'm just talking Sigs here and the guns I own. HD = 226st 40. CCW = 239 9{ 40 may be better}. Range = X5 40.

I have 2 of the 3 with a P229 9mm and a SigPro 2022 9mm. Last on the list is a Kahr PM9.

HD/Range: 226r or 220r, either one with DAK & a light affixed.

Carry: 229SAS Gen1

Always Carry: Kahr P9

hd hk p7
ccw walther ppk-l .32
range sig p210 9mm/.22lr

Range: Beretta 98 Combat
Home defense and CCW: SIG-Sauer P239
Historical archetype: SIG-Sauer P220

Glock 23
HK P7
SA 1911A1