"Teh sex" is a retarded way of saying something's "awesome" or "really, really good."

And Firesky, you did not create the word "sexi." You've been "saying it, like, forever"?!?! You're what, 15? It's a variation of the word "sexy" and only people who enjoy looking stupid use it.

www.urbandictionary.com (WARNING - WILL MAKE YOU STUPID)