I've always been told that you should promote what you have a true passion and love for and if that was going to be put into a niche for me it would be panties, thongs specifically
Also, I think male masturbation toys are a great idea becuase you get to use a physical product on yourself to enhance pleasure.
Webcams seem too general for me and even though there are specific niches that's what I'd have to focus on not just a general webcam.
I don't buy into the dating niche because I'm married, so that's not much of an interest to me
Let's keep the ideas flowing...