You get a 50,000 word draft for a novel that might turn into a publishable book!

This may seem silly, but in terms of actual, tangible/physical rewards, that’s what you get for winning. However, looking for tangible rewards in NaNo is like going to the beach because you want to breather high-humidity air: completely missing the good stuff.

Here’s what I’ve won year after year of winning NaNo:

1. An unimaginable sense of accomplishment. Seriously, even though I’ve never done it, I imagine this is what it feels like to run a marathon or climb a tall mountain. You wrote a book. Just like J. K. Rowling, Stephen King, Lewis Carroll, Miguel de Cervantes, all your favorite authors… This is something few people achieve, just by finishing a draft you’re in an incredibly small group. You’re elite.
2. A renewed view of literature. If you like to read (and I bet you do, since you know about NaNo), you’ll understand the creative process of writing like never before. Even if you don’t win, you’ll see how hard it is not just to come up with ideas (which are a dime a dozen) but to actually put them in action. Most people in my region start out very hyped about writing only to realize that their precious idea carried them for a thousand, maybe two thousand words. Even if you write non-fiction, you’ll see how hard it is to keep going, the paradox of having every possibility before you and having nothing to write about. You’ll respect good writers as you never thought possible. (see George Anders’ comment for a good example below)
3. This is more of a personal thing, but might be true for someone else. A few months after winning my first NaNo, I was talking with a friend about a certain problem in my life. I just wanted to vent, to whine for a while. At some point in the conversation, this friend told me “well, but you *did* won over that novel thing right? I bet that tenacity will help you here”. Suddenly, it dawned on me: if I could write 50,000 words in a month, what else could I do? How many other things I never did or tried just because they were “too difficult”? I realized that many other quests and problems in life are never solved because they are deemed “too difficult” from the start and never looked at again. Willpower is a finite resource, yes, but it can be managed, focused and applied in a smart way. You’ll find that, if you can write 50k words, there are many other things you can do. Of course, not every problem is solved by throwing more man-hours at it, but many do. Learning languages, programming, doing exercise, reading x books per year… many of these success stories have a common core of applied willpower which can be trained during NaNo

So, what do get for winning? A lousy certificate and a funny feeling of power over yourself.