There is a very large number of items... Here are some from the top of my head:
* Boots worn by X-wing pilots, Rebel Fleet Troopers, TIE-fighter pilots and various Imperial crew were German "Knobelbecher" WWII-style jack boots, and West and East Germany continued to use these and variations for decades after the war.
* Boots worn by Han Solo and Imperial Officer were German WWII-era officer boots.
* Belt strap buckle use by X-wing/Snowspeeder pilots is used by the British military to this day.
* The "blood stripes" on Han Solos pants were
US Overseas Service Bars from a roll. They were otherwise cut in shorter pieces:, one stripe equals six months of service overseas.
* The Rebel commandos on Endor in ROTJ wore lots of Army surplus: Swedish snow-jacket painted in camo, BDU pants painted camo, Vietnam-era US belt pouches, green canvas belt, canvas boots (not Israeli military but an older US type). The soft parts of the helmet were mostly a US flying helmet AN-H-15.
* Several pilots seen (mostly in the background) in ROTJ wore various soft flying helmets from the 1930s-50s.
* The Biker Scouts supposedly wore the same boots as the Rebel Commandos wore but covered.
There were several extras at Medal Ceremony in ANH that wore only British and US miilitary gear, but those garments were probably rented.
There is also military gear that people have thought were used, but which were actually copied in other materials:
* The X-wing/Snowspeeder pilot and TIE Fighter pilot helmets were
cast from modified moulds of a APH-6 flying helmet, size large. Vacuuformed ABS.
* The Navy Talker helmet was copied in vacuuformed ABS, for use as Rebel Fleet Trooper helmets, Imperial Gunner helmets and Imperial Navy Trooper helmets with different parts on top.
* The pattern of British soft flying helmets were copied in simple off-white cotton twill and worn under Snowspeeder pilots' hard helmets.
