Think I have to ring in for the beholder as the secret handshake. Doesn't have to be the 10-stalk beholder (that'd be a pain). "Yet Another Fantasy Gamer" webcomic (very entertaining, I highly recommend it to everyone seeing this!) draws most of his beholders with just 3 stalks.
I think that, stylized, would be a great idea for the secret handshake.
The "end-it" presented in the article says nothing to me except "dragon tribal tattoo"...which I had hoped by now was sorely out of fashion. hahaha.
If I saw that, I wouldn't assume for a moment that it was a D&D gamer. And knowing, strictly from the article, that it came from 4e means that it is just a 4e-secret-handshake. Gonna have to wait a few decades before all of us pre-4e guys are dead.
I'm afraid I really don't have a good suggestion of my own. Kinda stumped. It could be a ton of things...but many of my ideas won't speak to 4e players...just as the end-it didn't speak to me.
Beholder, I think, might be your most edition-neutral way to go. Mind-flayers work too, but then, stylized you might get into it with some Call of Cthulu players. (a brawl breaks out in the midst of Gen-Con! lol.)
Yeah, beholder...or maybe displacer beast? An outline of a panther face with two barbed tentacles coming up over it? That could be cool too. Think I'd recognize that.
Just my 2 cp.
--SD