Rather than specializing in a skill you could specialize in a market or domain e.g. digital services for furniture manufacturers (probably not a domain you personally are familiar with, but just an example).
So far I've been finding myself bringing product marketing to companies that don't already do it (they bring me in to improve engagement and product marketing is the low hanging fruit). I really don't want to get pigeon holed into that though.
What about branding yourself as an "Engagement Consultant"? That's a more defined service with plenty of demand (probably) and doesn't quite pigeon hole you into one type of activity.
