First, I'm pretty sure it is against some law to own only one air rifle. The same "one" is not going to be the best choice for everyone, as our uses and priorities vary. A simple, robust build would be important to me, to minimize maintenance and incidence of repair, and accuracy. The one I would keep is either the RAW HM1000 (standard, not "X"), or the FX Royale 400. The Royale is, for me ironic, as no other FX platform would be on the list.