Well, I'm not sure if this is the right spot to post it, but hey, there was the 'Hidden Equipment' thread, so why not...
I was playing on a private server on my warrior, who has Tier 6, and I found this:
It's on both sides of the helmet. Looks a lot like the Half Life symbol, does it not? :O
I did a search, and couldn't find this, by the way.