If you can't be marked and you want intense sensation, then electrical play is for you. It's also the most sedate type of torture that I can implement during a session. What I mean by this is that I can calmly sit back, turn the dials and grin as you squirm and writhe at the ministrations from my little black boxes. There won't be any loud noises from a whip, or the sting of a paddle, but rather you, will experience a full range of sensation and I'll never tire.
My arsenal at the moment includes two TENS units, an Erostek box (with remote), and a zapping tennis racket. The TENS unit is what most submissives are interested in experiencing. I have a variety of attachments to use on your genitals mostly. The feeling can be a mild tingle to intense stinging as your muscles in the area contract uncontrollably. Of course, I am the one who controls this sensation via the control box. I highly recommend removing as much of your genital hair as possible if you're going to try this activity out. Body hair does not work well with electrical play!