I sometimes wonder about that myself: what makes 
me proud about a specific cel? Why did I buy it?

1. It's looks in their essence, simple beauty?
2. The scene it was used for was special
3. What you paid
4. The attention it gets from others
5. It completes something
6. You won it in a fierce biddin battle
7. It was your first
8. It's on everyone's wishlist
9. You got it as a gift
10. It was on YOUR wishlist^^
...

This one fullfills serveral of those criteria:

Point 1, 2, 7 (first YJ transaction), 9 and 10^^

Nyo^^
Anna (who snuck out of school through the 
backdoor like a pro ninja)