Off the top of my head I know a few. I will admit to pasting some entries here from Wiki.... but only because my tping would totally stuff things up. I knew these things beforehand!
Clark Gable.....flew bombing missions over Germany in B17's early in the American entry into the war. He was supposed to be a publicity asset and did in fact make a documentary on the air war. He didn't fly as part of a particular crew and did only a few missions BUT that was at a time where the American Air Force was suffering its highest loss rate and he didn't pick and choose "milk runs". The Germans knew of this and actually placed a bounty on his head!
David Niven....In the Army, a lot of what he did is still secret and classified!
Spike Milligan and Harry Secombe...both in the army.
Michael Caine....OK...not WW2 but served in Korea!
COMPO...served in the
Royal Army Ordnance Corps during
World War II, where he was injured in an explosion during a battle training course.
Peter Sallis...joined the
RAF. He was unable to serve as aircrew because of a
serum albumin disorder and was told he might black out at high altitudes. He became a wireless mechanic instead and went on to teach radio procedures at
RAF Cranwell.
Michael Bates...He was commissioned in the
Indian Army in March 1942. During
World War II he served in the
Burma Campaign as a major with
the Brigade of Gurkhas and was mentioned in dispatches in 1944. NOTE: You DO NOT mess with Gurkhas!!!
Yogi Berra... was aboard a landing ship utility used to provide rocket support in the bombardment on D-Day
Richard Todd...was part of the D-Day landings.....I think he was part of the parachute brigade that took Pegasus Bridge
Henry Fonda... in the Navy and won a Bronze Star
There are lots more. I know of one who served as a Beach Master on D-Day, but for the life of me, his name is a gaping hole in my aged brain!