Not sure whether it's just me or the source. I might as well post what I've experienced, because I may be listing two glitches in one go.
I used Axe Booster on a Sabretooth ["Slow" Speed weapon] and then found a sword [Zard to be exact. "Normal" Speed]. I decided to mess around with it a bit.
Now, not only did Axe Booster speed up the sword that I was using. But it also made it that of the "Fastest" speed rank.
I would take a video of it, but the server's currently down. :/
~HellHammer.