Excalibur !!
Why the heck did not the Last Knight do anything special with the sword?
you would think they could make a sexy Autobot Lady of the Lake to give the sword to Merlin, instead of the clunky wizard staff?
They needed the "hero with the sword" on one hand and the "keeper of the wisdom" or "the thinker" on the other. This wasn't a mentorship pairing between Kade and the professor like that of Arthur and Merlin.
Maybe this is only my idea, but I think they needed a phallic symbol and that was represented by the staff. The staff represents then potency and thus the control or mastery over things, which the Decepticons were attempting to exploit with the staff as the key to destroying Earth and rebuilding Cybertron. The sword defended the staff/staff's mission/purpose and ensured thereby its proper use after briefly falling into the wrong hands.