My wife holds back my orgasms by pinching my nipples hard or by pulling on the nipple clamps and chains if I’m wearing them.
Conversely when she wants me to come she brings herself to orgasm using a wand or bullet. That always pushes me over the edge when I’m close.
Can’t think of anything 
There’s nothing that I’d be flat out too embarrassed to bring up I don’t think. I was a bit shy / nervous that she’d think me a bit weird when I was talking about my wanting to have her dominate me while I wear a muzzle gag / blindfold head harness though.
Happily it proved to be unnecessary and she enjoyed it. She even likes to wear it herself sometimes.