Limited to WW2? The M-1 is heads and shoulders above all others, leaving us to quibble over the merits of the various bolt actions. If I had to go to war with any of them, the Jap Arisaka type 99 would be my choice. For many reasons:
The gun was simple and easy to manufacture, it was enormously strong, it was totally reliable, it was accurate enough, and the sights were surprisingly quick and easy to use once you got used to them. The firing/safety/ bolt assembly consisted of only seven parts. The bolt cover was a stroke of genius, if you learned that whacking it with a hammer in the right spot pinched it, and it stopped rattling.
And then there was the ultimate stroke of genius, that chrome lined bore. It didn't rust, even in the tropics with corrosive ammo. Of course I am talking about the good ones, not the last-ditch junk. The Germans had the same problem..
And Excuse me for saying "Japs" instead of Japanese. When they admit to the Rape on Nanking I'll clean up my language.