As long as equipped creature is tapped, tapped creatures you control get +2/+0.
As long as equipped creature is untapped, untapped creatures you control get +0/+2.
{3}: You may tap or untap equipped creature.
Equip {3}

• Number: 264
• Rarity: R
• Type: Artifact
• Subtype: Equipment
• Mana cost: 4
• Color: Artifact
• Artist: Greg Hildebrandt