JediMasterEd wrote a neat story about Spike reflecting on his feelings for rarity, vis-a-vis gems.

The story does something that a lot of stories fail to do, which is to say, making use of a character's species in order to enhance their characterization, rather than using their species in the place of characterization.

What do I mean by that?

In this story (which I'd recommend you read - Beneath Your Feet, What Treasures is only 1,444 words long, and has a very interesting idea behind it) Spike has a small, personal hoard of gems that he keeps secret from everyone. He doesn't have to keep it a secret, but he wants to keep it a secret. In part, this may be dragon instinct, but in part, it is also because he wants to feel like more of a grown-up, and he fears that if Twilight found out about it, she might think it was... cute.

Ugh.

And that's not to mention what Rarity might think of it, especially given that its centerpiece is a gem some folks might remember from season 1...

The thing is, what is great about this story is not that he has a hoard, but that the meaning he ascribes to his hoard lends him characterization. He is not a dragon who happens to be a person, but a person who happens to be a dragon, and his view of his hoard is colored by being a dragon. But he isn't a slave to his instincts, nor is he trying to resist them; rather, he is who he is, and who he is is a single, organic whole. A pony might not think of things in quite the same way that he does, nor make the same sort of relationships between gems and people, but he does, and in a way which is consistent with him as a person.

It was a very interesting idea that got me wondering: what stories have you seen that have done a good job of making use of a character's species in order to aid the characterization of them as a person, rather than simply using their species trait as a substitute for individual characterization?