I already did one for AJ (was there any doubt I wouldn't?) which you can see here.

 

http://mlpforums.com/topic/13879-12-reasons-why-your-favorite-is-best-pony/?p=1591554

 

In addition to being a huge AJ fan I am also as many of you know from my sig and the Luna fanclub thread I started on here a bit of a LUNAtic so it is time for me to go into fanboy mode once again, this time for the princess of the night.

 

1. Luna is not your typical princess character: Luna is very humble down to earth, and dosen't seem to care much about protocol.

 

2. Luna has this mysterious vibe to her: A little air of mystery can make for a very interesting character and Luna is proof of this. We know that she became Nightmare Moon in part because she was jealous of her sister but we don't know what was going through her mind during this time. We know that there is more to the story but we don't know exactly what.

 

3. Luna is strong yet vulnerable at the same time: As the princess of the night she is one of most powerful beings in the MLP universe yet is also struggling to regain the trust of her subjects after her reform as the former villain Nightmare Moon.

 

4. Has a touching redemption story: I am a sucker for a good redemption story and Luna has one.

 

5. Is both cute and sexy at the same time

 

6. Tabitha St Germain is an awesome voice actor

 

7. The royal Canterlot voice provides for some awkward and hilarious moments

 

8. Can actually enter ponies dreams

 

9. Acts as a counterbalance to Celestia: Celestia is a good princess and pony but she does have some clear bias in favor of Twilight who we know is an awesome pony but is not perfect. We see some subtle example of Luna sort of playing devils advocate to Celestia though I wish we could see a bit more of it.

 

10. Is one of the most relatable characters: Luna is struggling to fit in as she readjusts to a society where many ponies still hate and fear her due to her past actions as Nightmare Moon.

 

11. Luna has a darkness that is usually reserved for villains and anti heroes: as the princess of the night she will always be associated with darkness but her character represents that darkness need not always be about evil but that it can also be beautiful.

 

12. Is one of the secondary characters with the most amount of potential: there are so many directions they could take Luna's character including the nature of her relationship with her sister.

Source: 12 Reasons Why Your Favorite is Best Pony