After posing the question yesterday, here’s the gun I would want if I had no restrictions on ammo, availability or money:
FG-42 (FallschirmGewehr Model 42)
The top is the first model — easily distinguishable by its sharply-raked pistol grip, stowable cruciform bayonet and milled receiver — and the lower is the second iteration which was sturdier and lighter, with a stamped receiver and no bayonet.
I would take either in a heartbeat.
Update: As do Readers Frognot and Preussenotto, from yesterday’s Comments, thus showing themselves to be connoisseurs of fine weaponry.