i got a smith&wesson model 422 for a 100$ and is my favorite gun to shoot, because i can hit what i'm aiming at without flinching from the recoil. on the other hand i have a colt gold-cup national match 1911 .45 that i love to shoot as well, just cost 4x as much!
I love my .22lr Rugers. MkII and Single Six are the most comfortable. There's something about making tiny, precise holes in paper that just feels right, and I'm too cheap to buy a S&W 41.
Otherwise it'd have to be a 5" 1911. I love obsolete handguns.
Compact 9mms and 45s are the most enjoyable for me. They strike a nice balance between weight and accuracy. After those, it would be a 22lr revolver if plinking at cans or a Hi-Power/Bersa HC if target shooting.