I think you can do great with any niche as long as you are really into it. Otherwise it's too much like work for you -- and it will be obvious surfers when you don't get it right.
Here's a 50/50/10 femdom program for our site Humiliatrix.com, administered by ccbill. It's a fun unique site.
Just created the affiliate program this weekend so it is fresh and hot:
http://www.humiliatrix.com/webmaster...liatejoin.html