Weapon and Armor Proficiency: Druids are proficient with the following weapons: club, dagger, dart, quarterstaff, scimitar, sickle, shortspear, sling, and spear. They are also proficient with all natural attacks (claw, bite, and so forth) of any form they assume with wild shape (see below).
Druids are proficient with light and medium armor but are prohibited from wearing metal armor; thus, they may wear only padded, leather, or hide armor. (A druid may also wear wooden armor that has been altered by the ironwood spell so that it functions as though it were steel. See the ironwood spell description) Druids are proficient with shields (except tower shields) but must use only wooden ones.
A druid who wears prohibited armor or carries a prohibited shield is unable to cast druid spells or use any of her supernatural or spell-like class abilities while doing so and for 24 hours thereafter.
Questo è quello che dice il manuale. Notate (in grassetto) che parla solo di armature e scudi proibiti. Non di armi. E non c'è scritto che le armi scelte debbano essere per forza quelle della lista.
Ergo, può usare anche altro, con il limite però nei confronti del metallo che rimane una inderogabile Master's Choice.