A421: Favored weapons have few mechanical effects. You can certainly initiate any maneuver you choose while wielding any melee weapon. The major effects are the Blade Meditation feat, the Swordsage's first Discipline Focus ability, and restricting a few of the schools' associated feats. All relevant feats say "while you wield a favoured weapon of School X" somewhere in their description. Stormguard Warrior requires you to be proficient in at least one of the discipline's favoured weapons, but doesn't restrict the weapons you may use with it. Shards of Granite, on the other hand, requires favoured weapons for all three maneuvers, and this is noted in the feat's benefit text.