One of my favorite jobs I've ever had was in product marketing. I was pretty new in my career and in my first true management role and I felt challenged like no other point in professional life up to that point. The first thing I remember about that job was how high a profile it was in what was a very large company. Having that kind of executive exposure in my mid 20s was fantastic and scary all at the same time, but it accelerated my learning and gave me a respect for what marketing did well beyond my years of experience. For those that haven't been exposed to a product marketing role here's a quick overview of what it's like.
Product marketing is one of the most comprehensive roles in the marketing construct. To excel in the role you have to understand your product intimately as well as understand the market and how it's moving around your product. It's one of the few marketing roles that depends on all 4 Ps (product, place, promotion and price) consistently and often put you in direct control of all of them. Product marketing can take two forms - one where you manage an existing, in-market product or one where you are tackling the development of new products and getting them in market. Regardless of the slant the responsiibly of being "chief cook and bottle washer" for a product that a company depends on for revenue is a tremendous opportunity for any marketer.
Product marketing also exposes you to all parts of a company's business and the functional aspects that it takes to run it. I was regularly in charge of cross functional teams that included parts of the business I would have never seen if I wasn't in a product role. This kind of exposure make you a better marketer plus a better businessperson. In addition to the exposure, it takes a solid understanding of those roles in order to get them on your side and keep everyone in sync. Sometimes you will feel like you will have to know their job better than them, but the more you understand their issues and motivations the better set you will be to get all the things done
If you're looking for one of the ultimate marketing challenges think about a product marketing role. It will help you grow in ways well beyond marketing and give you new insights into how marketing fits into a business.