Hawkeye's Bow + Kelpie Guide + Forensic Researcher Combo

All permanents on the battlefield (Hawkeye's Bow attached to either Kelpie Guide or Forensic Researcher on the battlefield and Kelpie Guide and Forensic Researcher without summoning sickness on the battlefield).

Activate Kelpie Guide by tapping it, targeting Forensic Researcher.

If Kelpie Guide has Hawkeye's Bow attached to it, Hawkeye's Bow triggers, dealing 1 damage to each opponent.

Resolve the Kelpie Guide ability, untapping Forensic Researcher.

Activate Forensic Researcher by tapping it, targeting Kelpie Guide.

If Forensic Researcher has Hawkeye's Bow attached to it, Hawkeye's Bow triggers, dealing 1 damage to each opponent.

Resolve the Forensic Researcher ability, untapping Kelpie Guide.

Repeat.

Infinite damage