There are so many memorable scenes in the Indiana Jones series. Whittling the list down to just one is a tough enterprise and it will likely be different for everyone, but it was easy enough for me to pick my favourite moment and scene stealer from the Raiders of the Lost Ark because it was unexpected and funny.
When Indiana Jones is confronted by a confident, Egyptian swordsman, whipping his sword around in a flashy, arrogant display, Indy, with a wearied look of fatigue and disgust, simply pulls out his revolver and blows him away. The kill was unexpected and effective in its simplistic swiftness, and it differed from more customary movie scenes of hand-to-hand combat that tend to ensue when two foes face-off. Rarely does an action hero simply act swiftly by using his gun to take out the enemy. Rather, the hero often tosses his pistol away out of some silly sense of pride, choosing instead to duke it out rather than just shoot someone.
The scene has become rather iconic, gracing several "best of" lists like the most memorable movies scenes of all time and the best improvised/unscripted scenes in film. The scene was improvised by Harrison Ford after he grew tired of so many takes in the blazing 130-degree heat of Tunisia. Originally, the script called for a lengthy battle that would have taken about three days to shoot. Ford was experiencing upset stomach issues and suggested that they shoot with just a gunshot, and the change ultimately made the final cut. It has become one of the most famous scenes in the series and among the most memorable in film.