The Indiana Jones movies are full of Easter eggs and small background details many people missed until they were pointed out online, but in Indiana Jones and the Last Crusade there's a moment that we all saw but didn't quite register.
It has to do with the scene where Indy avoids a saw blade trap by falling to his knees then rolls out of the way of a second blade like an archaeological ninja.
So why is this scene so horrifying? I'll let Cracked's Jordan Breeding explain:
In one section of the cave, Indy is told "Only the penitent man will pass." Knowing this is some sort of Biblical riddle (and that apparently faith makes you better at solving riddles), Indy struggles for an answer before, at the last possible second, he realizes he must literally kneel down "before God" and ... do a kickass forward somersault?
Why would a penitent man also be a skilled tumbler with lightning-fast reflexes? Is the 11th Commandment that one must become an expert in P90X so you may answer the call? And how the heck did Indy even know that would happen? The answer, it appears, is that he would have been fine if he'd just knelt -- the second blade would whip in front of him, though close enough to graze his knees. So what's the point of it?
Let's put it this way: If your idea of being penitent before God looks like this ...
... you'll be fine. But if it looks like this:
That blade will lop your f$%#ng head off. It makes perfect sense if you notice the title of the film, and the fact that the ancient knights protecting the grail (including the one who'd been magically kept alive by it for centuries) were from the First Crusade -- that is, a war to retake the Holy Land from the Muslims who'd captured it more than four centuries earlier. So our Crusaders were forward-thinking enough to ensure that only true Christians would get through, and that intruding Muslims would be killed on the spot even if they figured out the riddle.