If I could only have one hand gun I would want it to be a 44 mag. You can load it for what you want to do with it. From shooting light lodes for fun to max loads for taking down just about any thing where I hunt. It will shoot cast bullets as well as any factory bullets. It will shoot bullets from 180 gr to 300 gr. If you run out of ammo you can always use it as a club and beat something to death with it.
In a rifle it would be the 358 Winchester. Properly loaded it can take any thing in this country with out being to punishing to the shoulder. It' is good out to 400 yards and that is farther than I will ever shoot at game. You can also down load it and use it on small game or do some light fun target shooting.
Shot gun would be a 12 gage. Check back with me in a couple years and that may change to 20 gage. I am really getting down on recoil.