Robot Free Skype.
Make it possible to opt out of Robots (aka Cortana).
Sean Ellis commented
In Settings > General, under sub-heading "Corana" there are switches labelled "Suggestions" and "Personalisation". I have turned both of these off, and have not been bothered by Cortana.
It would be good to be able to remove Cortana from my contacts list though. It's not a contact.