A bit over the top but:
Stealthily replace the enemy stronghold's shipment of arrows and bolts with cleverly disguised immovable rods, and set the command word to activate them to be someone shouting the word "FIRE!" Congratulations, you've just disabled all of the enemy force's archers.
I really like that one. Expensive though... A nice touch would be to make the
deactivation code something really difficult. (like, they only deactivate at
your touch) After you win the battle, the hundreds of floating rods will be a symbol of your cunning and might for centuries to come.
Guards along the stronghold walls will also likely use them as a convenient coathanger or place to lean against. Lazy guards...
That's for the millionaire wizard wizard who wants to send a message.