Singing Short Sword offhand?
 

So, I'm unable to check it myself at the moment, but I heard a buddy say they ninja patched this in the newest one without saying anything?

I don't see anything about this in patch notes, but its supposed to be part of the October 2001 patch (as per Wiki timeline and item page)

it allows you to invis with epic in offhand now. appears to be fully functional epic in offhand.

Its gone
Time to get better, idiot