My favorite is the M1 Garand. As George Patton said: "The greatest battle implement ever devised."
The M1 carbine has a reputation as a fun rifle to shoot, and it is, but the Garand is just so neat and smooth. Excellent, reliable and effective piece of engineering, wonderful dial-in sights, the gas operation tames the recoil, still a big boy round, the Garand ping from the ejected clip. A Cadillac of rifles (though like the caddy a bit heavy). Most of my surplus ammo is Lake City or Greek surplus which I have stocked up on while supplies last (and will likely get some more).
The Carbine is 2nd, and an awful lot of fun to shoot and probably more in a plinking environment. The CMP '43 Inland I have has all of the late rebuild features with the potbelly stock and much improved sights, but I haven't got to the range with it yet. The '44 is all early features and shoots fine.
Among the bolts, my favorite is the Enfield No. 5 Mk.1. It is my most accurate Enfield (the 1917 is really a bit rough but it did see action in WW1, and the No. 4 is OK). I have a replacement butt pad for the original leather one that had expired and it seems to mitigate the recoil. I find it pleasant to shoot. The rest of the bolts go out here and there as the mood dictates.
Among the pistols, the 1911 Milspec is the tops. You just have to feel the grip and John Moses Browning's spirit to know why

Most of my small "accumulation" is based on shooters with history. About 1/4 are gifts or inheritance. Some are rough, some are in excellent condition like the Garand. Since none are truly collectible in the antique roadshow sense, it's actually a cheap hobby. My latest, the 91/30 was $65 and being built in 1941 -- the stories it could tell. From the darkest days to maybe the streets of Berlin. It was also rearsenaled -- killing collector value -- but looks fantastic.
Charon