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Equipped creature gets +1/+0 and has "Whenever this creature attacks, you may sacrifice Sunfire Torch. When you do, this creature deals 2 damage to any target."
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)
The source of the damage is the equipped creature, not Sunfire Torch.
You don't choose a target for the triggered ability granted by Sunfire Torch at the time it triggers. Rather, a second "reflexive" ability triggers when you sacrifice Sunfire Torch this way. You choose a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.
