.44 mag or .480 ruger would be my choices before jumping up to a monster like the .500 S&W etc...really I think, the .44 would be my standard and the .480 kinda my big version, I'd take the .480 over the .454

I think pepper spray is probably the best way to go though. They tell you to bang pots n pans vs. firing a round into the air...and spray supposedly is more effective. I'd say have both, but up to you. Think a gun makes you feel safer....