Attack Trigger

Attack Trigger アタックトリガー (Atakku Torigā)
Japanese Wiki: 851

Attack Trigger is a term used for creatures that have an ability that triggers when they attack.

Details

It first appeared on creatures in DM-02 Master of Evolution and DM-02 Evo-Crushinators of Doom.

It is usually templated as "Whenever this creature attacks, EFFECT" or "Whenever your creatures attack, EFFECT".

As it can trigger on each attack, it has the advantage of being used each turn repeatedly.

However, there is a one turn delay in using the ability (due to Summoning Sickness), it is often shunned in comparison to a Come Into Play ability. For example, while Bronze-Arm Tribe is a popular and much used card, its equivalent with an attack trigger; Silver Axe was not used in competitive settings. The only exceptions are Evolution Creatures and creatures with Speed Attacker.

The ability triggers immediately after the attack is declared, so occurs before the opponent can block or use the Ninja Strike ability. Therefore, with cards that can destroy creatures via their Attack Trigger can prevent your opponent creatures that have Blocker from blocking it, and a card such as Horrid Worm can discard cards from your opponents hand so they cant use Ninja Strike. It also activates regardless of the creature being blocked or not, so creatures with powerful Attack Triggers along with a Come Into Play ability combined with it, Speed Attacker or an Evolution Creature with such abilities are extremely difficult to stop.

Hypersquid Walter

Water / Creature / Cyber Lord / 3 / 1000

■ Whenever this creature attacks, you may draw a card.

As Power Attacker is a static ability, it is not considered to be an attack trigger.
In a narrower perspective, it is referred to as the trigger source and the attacking creature being the same, and does not include the trigger "When other creatures attack". Since Cross Gears' trigger abilities are not directly giving the crossed creatures Attack Trigger abilities, but are triggered when the crossed creature attacks, one should be careful when referring to this narrower perspective.
Cross Gears such as Master Weapon - All Yes or Bajula's Soul can give attack trigger abilities to the crossed creatures. This can be useful as they are trickier to remove from the battle zone.
Since Speed Attacker can allow the trigger to be activated on the turn the creature is summoned, it is very compatible with Attack Triggers. GENJI Double Cross, Blastdragon' strength comes from having both of these abilities. Since Power Attacker is a static ability given while attacking, it's compatibility with it is good too. An example of this is Onimaru "Head", Victory Rush, which has the Speed Attacker ability as well. The same goes for Evolution Creatures.
Attack triggers make Chump Blocking useless as the effect will pull off regardless of if the creature is blocked. Even if the creature is blocked and destroyed, the effect will still pull off and the defending player will still lose advantage, so blockers are impractical against creatures with strong attack triggers and high power.
There are cases where Attack Triggers increases the size of your opponent's hand. In those cases, Shinobi added to the hand after the declaration of attack are still able be used. This is because Ninja Strike is triggered regardless of which zone the Shinobi is. That means that they can come out with no problem as long as they are in the hand when the Ninja Strike ability resolves.
There are cases where Attack Triggers reduces the opponent's shields to 0 during the attack declaration. In those cases, as long as the attacker is not blocked or removed, a direct attack is established and goes through.
Creatures such as Almeric, Spirit of Prophecy and Terradragon Balgazarmas grant attack trigger abilities to each of your other creatures.
While it is not used as a term in the card game, Benny Haha uses it to explain the ability of Stained Glass.