~Jedi Weaponmaster/Master/Watchman~
When a Knight has proven extreme skill in matter of the Force, wielding their lightsaber, or being a skilled diplomat all around, not only do they get new appropriate ranks, but better lightsabers (or new lightstaffs) and a new cloak. Traditional Jedi robes do little more than protect the wearer from the weather, but these new robes are ridden with the Force, and can even make oneself stronger.
A Jedi can become a Master if and when they successfully train a Padawan into a Knight. Further, not all Masters are special-ranked (Guardian/Consular/Sentinel)-in fact, not many on the Council itself were; only Yoda, Windu, Saesee Tiin, Plo Koon, and few others. Obi-Wan Kenobi might have, being he was THE MASTER at Soresu, but the title was never officially granted to him. Anyhow, Jedi Masters receive nothing else except the same cloak as the special-ranks and the chance to make electrum lightsabers, like Mace Windu.
A Jedi Weaponmaster is unparralled in wielding their lightsabers. Jedi Masters are supremists at the Force. Jedi Watchmen are all-around good, but aren't the best in either category. It's probable Yoda and Kenobi were Watchmen, while Windu was a Weaponmaster.