Raiders of the Lost Ark, in which Indiana Jones went after the Ark of the Covenant, currently has an 8.5 on imdb.com. It's the highest rating of any film in the franchise, with The Last Crusade -- in which Indy pursued the Holy Grail -- at an 8.3. The other two films don't rate anywhere near that high.
So the message is clear: Indy needs to go after something Biblical. Nothing else has that kind of emotional impact. Only, what's left for him to look for?
Answer: The Staff of Moses.
Moses' staff started off as a simple shepherd's crook, but went on to become the basis for every sorcerer's staff or fairy's wand that followed. Seriously, why else is a stick the symbol of magic? Why not a glove, or a kerchief, or a gemstone? Because Moses invented the magic wand.
The Blue Fairy, the Fairy Godmother and Tinkerbell … Gandalf, Dumbledore and Jafar… from Hermes and Circe of myth to the magician at a 5-year-old's birthday, each has a wand or staff of some sort. (As for Hermes' snake-entwined staff becoming the symbol of doctors and healing, that's also Biblical in origin; see Num. 21:8-9).
Now, Moses's staff has three main powers. One is its command over water. We read about it turning the entire Nile to blood (Ex. 7:19-20), splitting a sea (Ex. 14:21), and drawing water out of a boulder (in both Exodus and Numbers).
Another power relates to its control over simpler animals. In the second and third plagues, it calls forth infestations of frogs (Ex. 8:1-2) and lice (Ex. 8:13). Even its very first miracle is to turn itself into a snake (Ex. 5:2-4); it repeats this transformation in Pharaoh's court and devours his magicians' snake-staffs as well (Ex. 7:10-12).
The last power of the staff would be why the Nazis want it (it's always the Nazis). In one battle retold in the Torah, the Israelites win as long as Moses holds the staff aloft (Ex 17: 9-13). Of course the Nazis would crave an object that helps them win wars with ease.
So, Mr. Steven Spielberg, I think you see the cinematic possibilities of the Staff of Moses for the next Indiana Jones film. Imagery-wise, we're talking about water effects, swarms of small creatures, and an epic battle. But this time, the object of the quest goes right at the heart of Indy's character, because it's both what Indy wants -- and fears -- most. How epic is that?
The other object in the Torah that would be worthy of an adventure is the Urim V'Tumim, the High Priest's gem-studded breastplate that could foretell the future and reveal secrets. But that's harder to explain … we can save that for the sixth movie.