I got interrupted earlier, but if you want the coolest get a 6.5x55 and shoot 140’s.
+1, with NP 140s. Rifle? I prefer CRF actions, so an M70, custom Mauser or a CZ550.
A .280, .280 AI, or a 6.5-06 would also be cool.
Easiest choice? An M70 Featherweight in .270 or .30-06.