I love dressing my boy up before playing with him. Having a human barbie doll is rather a lot of fun.
Also on my list is spanking and biting and just generally playing rough. Boy doesn't like the biting so much though, I tend to bite a little too hard sometimes and cross the line between pleasure pain and pain pain. I always feel really bad when I do and it completely kills the mood.
Also, anything that will leave marks. I like having a visual reminder of the fun that was had. Always makes me horny again the next time I see them. And pictures, I love taking pictures. And I love it when he masturbates for my viewing pleasure.
Ooh, and begging, begging is good. I like it when I can make my boy beg for more or just be vocal in general.
As for things I've never tried I have a big thing for needles and love love love getting piercings and think my boy giving my temporary ones in play would be rather fun. Unfortunately for me he is seriously afraid of needles and even being around them creeps him out so I doubt it's ever going to happen.