In The Hobbit Trailer: This shot actually comes from one of the optional endings fans can choose to edit their own trailer - but it's still significant, and resonant.

Here, Balin mocks Bilbo's weapon, "I'm not actually sure it is a sword." We know it's not - it's an elf knife, which happens to be a perfect sword-like size for a hobbit.

We also know that far cooler than Balin realises, because…

In The Fellowship Of The Ring Trailer: We see Sting's power - to glow whenever there are orcs are close. Not so shabby now, is it?

Also, notice that neither Bilbo nor Frodo fully unsheath the blade. In fact, they show around the same amount of sword to the camera. Again, Jackson is reminding us that these films are a bit linked.  

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