Originally Posted by ZachRome
Anything works haha whatever your willing to give
Do you reload? If so, the skys the limit. Any caliber is good for plinking.
Otherwise, if you're going for cost efficiency, I suppose the .40 S&W is cheaper ordinarily than the .45 ACP. I don't particularly care for the snappy recoil of a .40, but I've also only shot it in a compact sized gun. A larger framed gun would diminish some of that felt recoil.
I've never actually had the pleasure of shooting a 1911 but I've heard their fun factor can hardly be beat, and I prefer the recoil of a .45 over a .40.
In terms of platform (already mentioned the 1911), I like the S&W M&P series a lot. They fit my hand perfectly, and they're a joy to shoot.
Or you could go the opposite direction in terms of caliber and go with the .17 HMR. I've never shot one, but I've heard good things. Couldn't begin to tell you how expensive the ammo is, as I have no idea.
Hope this was somewhat of a help.