From A Wiki of Ice and Fire
They use slender swords that are edged and balanced for the thrust. The bravos fight from a sideways stance with weapon extended.
It is said amongst the Braavosi that the night belongs to bravos and courtesans. When night falls, good citizens of Braavos retreat indoors, closing shutters and barring doors. Bravos swagger through Braavos in their parti-colored finery, looking to pick fights and prove their skills.
Most will fight with little cause or no cause. Anyone carrying a sword after dark in Braavos can be challenged to a duel. Simply placing a finger on the hilt of your sword while facing a bravo is akin to challenging them. Bravos never bother anyone without a sword. They are known to duel by the Moon Pool at night. Dying bravos often find their way to the House of Black and White to hasten their ends.