Goblin Sharpshooter, and Quietus Spike

Prerequisites

• Goblin Sharpshooter on the battlefield
• Quietus Spike on the battlefield
• Quietus Spike attached to Goblin Sharpshooter
• Goblin Sharpshooter does not have summoning sickness

Steps

1. Activate Goblin Sharpshooter by tapping it, dealing 1 damage to target creature
2. That creature dies from lethal damage due to Goblin Sharpshooter's deathtouch ability
3. Goblin Sharpshooter triggers, untapping itself
4. Repeat for each creature opponents control and whenever an opponent controls a creature

Results

• Destroy all creatures opponents control
• From now on, destroy any creatures opponents control at instant speed