ive got two .22's ones a 100+ year old pump action 22, looks like a mini shotgun that shoots 22's its fun.
then a sig 522, which is fun as hell, great quality, got a nice red dot, and its awesome for just going out and fucking around, accurate too, and it comes with a longer/better barrel if you do more target shooting, even with the stock barrel i can easily hit rabbits in my yard from 30-75 yards or so, and hit them in the right places.
and ive also got a 22 magnum henry golden boy, which i would recommend if you're only gonna have one gun,  22 is fun for fucking around, but just too limited, the magnum is accurate without a scope out past 100  yards, still accurate to 200, but with no scope its not much use.  i have a milk cartons i set out at 100 yards and can hit them every time with the iron sights.  get an oldschool looking scope and you will be set.  the magnum actually does some good damage, with a good hollow point rabbits explode, and i know people who use them to hunt coyotes.
and its still quiet and cheap enough to just go out and fuck around, plus the lever makes it fun.
a scoped, bolt action .17hmr would be sweet too, that might be my next gun.