Nocturne

Nocturne
From Marvel Comics

Talia Josephine "T.J." Wagner. The progeny of Nightcrawler and The Scarlet Witch. From an alternate reality, though. And a cool alternate, indeed. Not only do we get our favorite color chick out of the deal, she's badass with her super agility and skills inherited from her dad.

Also, she can possess other people. Yeah, make the joke. But since she also has some latent telepathy going on, you better be really careful what you think around her.

Don't get this Nocturne confused with the others, there were 3 others in the Marvel Universe, none of which are hot blue chicks. So if you go googling for more hot blue-retractable-tailed Nocturne action, it's not my fault if you end up finding some dude with a gun don't blame me.