Lightning Bug
The weapon referred to only as 'the Lightning Bug' is a piece of technology from the Generation 1 Animated Series continuity. It is a strange device that looks vaguely like a giant beetle on an altar; when the wings are moved into the proper position, it fires lightning bolt-like blasts of energy from its antennae.
The Lightning Bug was found on the dead Autobot colony of Antilla by a small group of Decepticons, including Megatron and Starscream. They took the Lightning Bug back to Earth with plans to use it against the Autobots. That plan backfired and got most of the members of both factions infected with Cosmic Rust. The Lightning Bug was destroyed afterwards.