Seems to be lots of credible evidence of the Japanese useing the Garand during WWII. I suspect largely because of hold-outs running out of ammo. It is amazing how long some of the Japanese fought on after the Island they were on was considered secured by the US.
The North Koreans and Chinese used a lot of captured M1 Garands during the Korean war. Lots of film footage and photos backing this up. The Chinese had lots of .30-06 to go with the M1903 and M1917 provided them during WWII and the Revolution, and useing M1s was natural considering the length of their supply lines.
On use of captured weapons by German soldiers - there is a book called something like "It Never Snows in September". It's another book on the war in Holland covered also by "A Bridge Too Far". In it a German paratrooper talks about how much they liked captured STEN SMG because the vertical mag allowed a lower profile when fireing from a laying position. Several pictures of German paratroopers carrying STENs in the Battle of the Bulge are available.