Off the top of my head, I can think of BFA Nightname, lick Hakaman being fake-Guardian aliases. BFA Sabrial was actually DarkFire if memory serves. I think BFA Bio/Mach and Angelous may have been fake identities too, but my memory is fuzzy on those ones. (I'm fairly certain Bio was) Plus Ceasar is an admitted alias, and that "Anima" guy who applied a few months back is a pretty obvious one. Flyer can be included technically too.
I know there are dozens of other ones that I either wasn't around for/can't remember too. I'm fairly certain Guardian alone could probably account for like over five fake siege identities. I think he had a UJ one too, but I forget the name. And I know he was RCB Hurricane, but I think it was a pretty well publicized fact that Hurricane was Guard.