As a writer with a technology background, I find apps designed for writing of more than ordinary interest. I’ve tried a huge number of them and have quite a few still installed. For the 2016 edition of NaNoWriMo, however, I basically chose one app and stuck with it most of the way through: Ulysses.
Most of my writing is done on a MacBook Pro, although I also use Linux from time to time (Ubuntu on a Dell XPS 13). The Mac has a huge number of writing apps available, more than any other platform. Scrivener and Ulysses are probably the best known and most widely used.
For NaNoWriMo, I found Ulysses to be virtually ideal. The chapter summaries (in the middle column) keep you oriented as you work through your plot development. Progress toward your daily word count is graphically shown in the upper right hand corner, which is quite motivating. The application is streamlined and powerful, but not overly complicated. It can be configured in any number of ways to suit your preferences (full-screen mode is especially nice).
Linux, unfortunately, lacks the Mac’s variety of writing programs. Still, there are options. For two or three days last November, I used FocusWriter, a nicely designed and versatile open source program available across platforms. It too offers a nice full-screen mode and a daily word count progress indicator, albeit text-based.
Ultimately, though, I felt most comfortable and productive during NaNoWriMo while using Ulysses.