Pour soapy water/shampoo into the urethra when I was taking a bath.
Put ants on it (they'll bite)
Pinch the scrptum really hard
And hitting it with one of those underwater jets in the bath. When I actually managed to position it just right I actually got similar results to the hand massager except the orgasm was A LOT better. As a matter of fact I would dare say that I have not had an orgasm that even came close to the bath-jet method. I couldn't even get up from the bath for awhile after I would cum.
I really need to try that bath-jet method again.
If anyone's curious and if memory serves me right, you'll need to first get your penis erect. Then have the bath jet hit the underside of your penis near the (but not on) the head.
The pressure needs to be just right also.