User blog comment:So-Pro Warrior/Special Sneak Preview of Season 2: Battle of the Ultimate Galaxy Savers: Master Chief vs. Commander Shepard/@comment-26074921-20130614034825/@comment-26074921-20130614045600

Using a weapon that he uses once or twice in his long career in very circumstantial occurrences to give him a better weapon is against the rules.

Its simply not a weapon he uses.