Well, maybe not quite "evangelizer," but definitely "Catechist's assistant." That's my judgment after completing "Deathly Hallows."
I was first alerted to the catechetical potential of this volume (and by extension, the whole series) when I read something (which I can't find just now, but it was in the final paragraphs of a page on the left hand side somewhere in the first 250 pages of the book) that could easily be used to illustrate the concept of "perfect" and "imperfect" contrition. Then there is a burial scene (no spoilers, don't worry!) involving a cross--not exactly a Christian confession of faith, since for many a cross has lost its true meaning and only stands for death, but still it's something. Then there is a Christmas Eve setting, in which people are in a church--as far as I remember, Christmases past in Harry Potter were only of the "jolly olde England" sort, with plum puddings and the like. At another burial (there's a lot of death in "Deathly Hallows"), the graveside words include the hope that the deceased is "happy now." There's even a little teasing over the blindness of fundamentalism contrasted with the clearsightedness of faithfulness. And if that were not enough, there is actual Scripture in the book, with one of the phrases being a rather central message. Most kids won't know it, but "Where your treasure is, there your heart will be" is from the Bible. And so is "the last enemy to be destroyed is death."
That's really not why I would say that Harry could be a Catechist's Helper, though.
There are also the examples of the Cardinal and moral virtues, and of the capital sins, especially pride, covetousness and anger.
But that's not all!
The central theme of the book turns out to be entirely consistent with the Gospel: "The one who seeks to save his life will lose it, and the one who loses his life will find it"; "no one has greater love than he who gives his life for his friends." (And no, that is not a spoiler; it's a tantalizer.)
To put it in terms of the Theology of the Body, "Deathly Hallows" is something of an illustration of the central theme of John Paul the Great, when he cites Vatican II: "Man can only find himself through a sincere gift of self."
So all those people out there who were afraid that Harry meant nothing but big demonic trouble, perhaps your fears helped the author to be even more boldly Christian than she knew. It's safe to come out, now. Harry Potter is on our side.