For me, it would be my .357 magnum revolver (GP100) and my Rossi .357 lever action carbine.
I choose those because I have them. I would upgrade the Rossi, but it would be a .357 carbine.
Romanian origin. Uses 7.62x54R (same as Mosin). Semi-auto designated marksman style rifle. 10 rnd mag. Hard-hitting, but quick to get hot when shooting quickly.
Threw in a pic of the 10mm Omega while I'm at it...