I would have to say a Surface. Here's my reasons:
1) I develop using Visual Studio. Granted they now have it on Mac, but my ecosystem that I develop for is Windows-based systems.
2) Office. Yes my office sub will work with Mac as well, but I like the Windows 10 style and can't wait for the Fall Creators Update.
3) Touch screen/Pen support. I want a Surface just for these features. I actually use pen and paper still to write down and draw out my thoughts. Having this on a computer would just be awesome.
4) Application Support. I play some steam games which aren't on Mac, or Linux sadly, so I need to be able to play them.
5) Community. The community is great, especially here. I asked a question about Office 365 in the store and wasn't shamed or that for the question. The people here are great.
Surface because it seems to be leading the trend of where mobile devices are heading.