Remington model 870 Super Magnum Express 12 guage shotgun

Remington model 700 chambered in .30-06 (I'm OK with a Winchester model 70 chambered in .30-06 also)

Any .22 LR

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That is a short list, but that covers the ground pretty effectively. Of course, I do have other firearms that I treasure and value, but the question was what is "esential," or at least that is how I interpreted the question.