In Harry Potter it is rather clear that Harry plays a Christ type role in the final book. Harry lays down his life for his friends, ends up in a train station type purgatory where he is given the choice to go back to finish the job. Along these lines I think that Neville Longbottom plays the typological role of crushing the head of the serpent found in Genesis 3:15 when Neville chops off Voldemort's snake's head. Call me crazy but that’s how I see it.
Here is a cool new blog that talks about the similarities between Neville and Sam in the Lord of the Rings that I found interesting. Link