I heard that those TENS systems that stimulate the muscles through electric pulses were supposed to be great. I bought one and tried it at different locations around my cock and balls. It has a bunch of different settings for duration, type of "massage" and intensities. I do have to admit that it felt very good stimulating my cock, but it never got me hard or to the point where I could make myself cum. I was rather disappointed in it for that purpose, but it does work well for a stiff neck or sore muscles!!!!
I had one for when I had some back problems. Of course that led to playing with it . My wife didn't like the shocking experience herself, however she enjoyed zapping me. She also had static wand that they would tease me with. I took everything they threw at me.