Ok, bear with me for a moment here, cause the story is a little longer than normal. When I first went to college, I went to Oberlin, in Ohio. It's a wacky school (I loved it) and in the house I was living in, they had large, unisex, communal showers. Now, they knew some folks wouldn't be cool with that, so there was this invention. Upright, it is an E, for Everyone. Flip it 90 degrees clockwise and you get an M for Men. Take the E and flip it 90 degrees counterclockwise and it's a W for Women. Upside down it is a 3, for Me, Myself and I, if you really weren't comfortable showering with anyone at all.
Now why would you want this on a necklace? Well, I've given it four rings, so you can orient it however you want. Feeling gregarious? Go for the E. A bit more introverted? Perhaps you feel more like a 3. Girl's night out? Looking for a girl? Go for the W. You've got the idea. The beauty of the thing, of course, is that no one will get it.