This just happened to me, so I know it works (the circumstances leading up to this incident are best left to the reader's imagination)
What you will need:
1) One (1) large rubbermaid (or nearest plastic equivalent) storage container. Mine was approximately 40 gallons with handles on each end that doubled as latches for the lid.
2) A bathtub/shower capable of accomodating the storage containter.
1) Once you have placed the storage container into the tub, turn the hot water on all the way (it should work with cold, too) switch the shower to as fine a spray as possible and aim the entirety of it into the storage container as if you mean to fill it with water (which was my intention).
2) Wait a bit until it's about one foot full.
3) Stick your hand in**.
You should get a very powerful jolt of static electricity. I repeated this three or four times within a 5 minutes and got the same result each time. The shocks became less intense after I turned the water off, eventually disappearing.
Why does this happen? Well, you will notice that these types of containers often have a static charge, as do many other plastics (most nobably, Reynolds Wrap). Static charge is exacerbated by friction, and though you do not really recognize it as such when you wash your hands or are in the shower water does indeed create friction.
Ergo, the water hitting the sides of the tub and the other water serves to amplify the static charge of the container.
**Note: I do not recommend this step if you are very young, very old, are prone to heart palpitations or seizures, have a pacemaker, or in any other way have a dodgy heart or... any condition, actually.
In fact, don't do this.