For your entry concerning Indy's bazooka ambush and the fly on Belloq's face, there is an interesting additional item: not only does the actor not react to the insect, but the audio guy attempts to cover for him by adding two subtle buzzes - one on the right channel for its arrival, one on the left for its "departure". Best heard with headphones.

When Belloq and his men reach the town of Cairo after being swiped by Indy and the van with the Ark inside, notice Ronald Lacey's character Toht. In this entire scene you don't see his face, totally shadowed by his hat - his head doesn't even move! Was Ronald unavailable for filming and hired a double...?

The rolling boulder in the opening scene was actually 22 feet in diameter and was made out of fiberglass.

The scene in Temple of Doom where Indy cuts down the gong and jumps behind it to avoid being shot is actually a reject scene idea from Raiders, just like the mine car chase.

The German U-boat in this movie is actually a mock-up built for Spielberg's earlier movie, 1941. It's only the front half of the sub, so you never see past the conning tower in close-ups. When you see the sub in its entirety, it's a model, which was also built for 1941.