The latest is the Italian branch of the Wind carrier, who are giving away 3 Lumia 950 handsets daily from now till the 7th December for lucky subscribers who can enter simply by topping up their credit via their website or app.
On their contest page they write :
Recharge any amount, by credit card, PayPal and other payment method available from the App MyWind or wind.it. Each day will be drawn 3 lucky winners of the new Microsoft Lumia 950. The new Lumia 950 provides superior functionality, excellent design and the best experience with Windows 10. On the official Facebook page of Wind will publish the names of the winners!
Winning a contest for doing something you were going to do in any case seems like a pretty good deal to me. Read more about the contest at Wind.it here.