Warhound doesn't claims to change the face of FPS forever, -- though it does have a couple of very cool little tricks of its own -- rather it comes to the genre from a slightly different angle and shakes things up more through its general approach than through any one feature.
Warhound is essentially a mercenary career simulator. You'll play an ex-military guy who now works for hire, sorting out all manner of conflicts and disputes by way of a contract and a bullet, and the game treats the whole process as exactly what it is, a business. Missions can be largely taken in any order, and while some of them will further the overall story of the game, many of them will be purely for the money. And money it turns out, is very important indeed.