This might be a stretch, but what about when the outsider finds this out, but ends up being the anti-hero throughout the book? Sorry -- sleepy at the moment, but I was thinking of one of the Darkover Novels ... Two to Conquer, I think. Actually, there are all kinds of being chosen -- and rejected -- in that particular book. And I just mixed up Bard and Paul in my head. But I think the point I started out with was that there we have an example of several kinds of being 'chosen' and having that status taken away.

For me, I have to say that the first six Deryni books never seemed like a guilty pleasure, and I think that Kelson at least fits your 'outsider who gets powers' scheme. Of course, I was at school when I read those. Dunno how guilty I'd feel now!