Australian carrier Optus has an offer of a free Xbox One for people who purchase the Lumia 950 or Lumia 950 XL with a two-year My Plan Plus or My Plan Business contract for $80 a month or more.

Xbox One

Of course, "free" is a relative term in this particular deal. The offer from Optus (via WinBeta) states:

If you leave your plan early you will need to pay out the full remaining cost of your phone and the Xbox One 500GB, including any amount that Optus was going to cover.

So you have better stick with that contract if you want to keep your Xbox One alongside your new Windows 10 Mobile phone. The offer is also contingent on the amount of Xbox One consoles Optus has in stock, so you might want to move fast if you want to get in on this deal.

See at Optus