Wulfgar of Icewind Dale

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
If a creature you control attacking causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Magic Online Promos

Forgotten Realms Commander

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
If a creature you control attacking would cause a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Melee
If a creature you control attacking would cause a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Wulfgar of Icewind Dale's last ability affects only triggered abilities with conditions that are directly related to attacking, such as “whenever this creature attacks” or “whenever you attack with one or more creatures.” It does not affect triggered abilities with other trigger conditions, such as “whenever this creature becomes tapped.”

Wulfgar's last ability will cause its melee ability to trigger an additional time.