There have been a few sightings of Halo cosplay at PAX.
Master Chief is there (all be it a bit shorter than usual).
From @NinjaRTB‘s twitter feed.
Vic DeLeon of 343 is hamming it up with two Spartans.
From @vicdeleon‘s twitter feed
And the ever adorable Mini-Chief:
From @The_DrMouse‘s twitter feed
From @bsangel‘s twitter feed
From @LairdSVF‘s twitter feed