Gamera
At least for the U.S., U.K., Commonwealth forces almost anything from the end of the Second War World works. Plus some stuff that barely missed the war. The South Koreans were largly equiped out of U.S. warehouses.
For the N. Koreans and Chinese it depended on what the Soviets sold them.
The ROKs started out very lightly equipped. The US did not want them to invade the North and try to unify the country by force. Of course this is exactly what the North did in June 1950. After being well equipped by the Soviets who had no such qualms.
For the Red Chinese, in addition to what was sold or provided to them by the Soviets, or what they could produce on their own, they had large stocks of US equipment captured from Nationalist forces during the recently ended Chinese Civil War.