I have to say that, for sheer fun, the adult sized but mild .177's seem to be the best for me.
If its easy cocking, smooth shooting and accurate its a winner.
You might get a gun like that anywhere... You WILL get a gun like that if you buy a HW30, HW50, R7, many Diana's, etc. And in my limited experience a Cometa 400. The Walther Parrus is too powerful to be included on that list, but its an awfully nice rifle that I bought new for Wal-Mart money... Not broken in yet but already impressing, and easier to cock than my RWS 350 but in the same energy category.