Before I answer, I gotta give the usual disclaimer copout for these threads: "Why?" For example, for permanent bugout I would select a certain set, in prolonged financial hardship requiring a selloff I would keep a different 3, house-on-fire-grab-3-quick is different yet, and if there was some harebrained Limit Law I might select 3 different still.
That being said, since I recently went through the "financial hardship" thought exercise anyway, this is what I came up with:
Pistol: My daily G26. I've trained with it and carried it extensively. I really like it. Sure, my G19 is more "versatile", but the G26 is everything it needs to be and nothing more.
Rifle: Tough one. I've tried hunting the past 2 seasons and gotten skunked, so I might be over this requirement. In most of the above scenarios, the keeper is my LMT/BCM middy. In others, it's my Marlin Model 60 or Maadi. Again, the AR class I took lends tremendous value to the AR over my "untrained" platforms.
Shotgun: I'm really not much of a shotty guy. I'd really rather use the slot for a second rifle. In any event, my only smokepole is my 870 Wingmaster with a 30" full choke. I'd keep it but swap the 30" full bbl for a 24" with screw-in chokes.
Funny that my .22LRs do not feature more prominently in my list. I like .22LR and use a lot of it. I'd hate to be stuck with "just" .22 in many scenarios, given the choice.