During your Main Phase: You can send this face-up card to the GY; inflict 1000 damage to your opponent for each of your Standby Phases that have passed since this card was activated.
Rulings
Individual Card FAQs
Sending "Wave-Motion Cannon" to the Graveyard is a cost, so when you send it to the Graveyard, it's too late for your opponent to chain "Mystical Space Typhoon", etc., to destroy "Wave-Motion Cannon", because "Wave-Motion Cannon" is already in the Graveyard.
Your opponent cannot chain "Magic Jammer", or use "Dark Paladin", etc., when you send "Wave-Motion Cannon" from the field to the Graveyard. Your opponent CAN chain "Magic Jammer" or use "Dark Paladin", etc., when you first activate "Wave-Motion Cannon" (meaning when you place it face-up on the field).
If "Imperial Order" is active on the field, count Standby Phases as normal for "Wave-Motion Cannon".
You can activate "Wave-Motion Cannon" (place it face-up on the field) and send it to the Graveyard during the same turn, but it will not do any damage.
If the Standby Phase is skipped with "Solomon's Lawbook" or the turn is skipped with "Gamble", increase the count for "Wave-Motion Cannon" anyway.
You cannot use "Pyro Clock of Destiny" with "Wave-Motion Cannon".
Netrep Rulings
“Wave-Motion Cannon” counts the number of Standby Phases it was on the field when it is sent to the Graveyard by its effect.
If “Imperial Order” is active when “Wave Motion Cannon” sends itself to the Graveyard, the effect of “Wave-Motion Cannon” is negated and no damage is inflicted.
Netrep Q&As
Q: During Main Phase 1, can “Wave-Motion Cannon” be sent to the Graveyard for its effect prior to the opponent attempting to destroy it with a Set “Mystical Space Typhoon”? A: As the turn player you could claim priority and send the "Wave Motion Cannon" to the Graveyard, to which the opponent can then respond. This would not be true if you were to activate another card's effect during your Main Phase 1 first, like "Raigeki" for example, since they could then respond with their "Mystical Space Typhoon" in a chain to "Raigeki" and destroy the "Wave Motion Cannon" in the chain. The opponent would need to destroy your "Wave Motion Cannon" during your Standby Phase. Curtis Schultz, 01/25/2004
Q: If a “Wave-Motion Cannon” is on my field and I activate “Imperial Order” does it still get its counter during my Standby phase. A: “Wave-Motion Cannon” does not use Counters. If “Imperial Order” is on the field, “Wave-Motion Cannon” will still get its phase count, but it does not use physical counters like other spell cards do. bishop, 12/07/2003
Q: If “Imperial Order” were active after “Wave-Motion Cannon” was activated, when “Imperial Order” leaves play, does the turn count return to 0? A: No, its count starts when it enters play and leaves when it leaves play. bishop 01/05/2004
Spell|
Continuous