On April 25, 2002, Team Overkill submitted this trick:
One of our members found out that Master Chief is just like all the classic heroes of the 16-bit era. By pressing in on the left analog stick (crouch) at the top of his jump, Master Chief performs his "double jump". It's not much, but that little bit of height can get you on top of obstacles you could never have jumped onto normally.
This added boost, unmentioned (as far as I can tell) before this, might be enough to complete some of the in-progress tricks...