A bad-ass fucking pony from My Little Pony: Friendship is Magic. She'll make a dress faster than you, and whine about how you take long to do it. And laugh in your face like this. "BwaHA-HA!"
Guy 1: "Dude, Rarity was awesome in that last episode!"
Guy 2: "I thought Fluttershy
was pretty cool in it too."
Guy 1: "LOL"
A girl that is both smart and hot. It is rare to find a girl like this so thus, rarity.
Kara, Jason's date to HC
is a rarity.
This relates to the Pony "Rarity" from the series "My Little Pony: Friendship is Magic". It is a term given to a girlfriend or ex-girlfriend when she becomes super bitchy and complains a lot.
"Man, your girlfriend has been a real Rarity lately."
"Dude, I am so glad you dumped her! She was such a Rarity!"