The Spark Beetle is a robot manufactured by the military organization, G.U.N., and is a part of G.U.N.'s Beetle series of robots. It appears as an enemy in Sonic Adventure 2, Sonic Adventure 2: Battle, and Shadow the Hedgehog.
It is basically a Mono Beetle equipped with an electrical shield that is used as a means of protection from attacks. Trying to directly attack the robot while the shield is up will result in the player sustaining damage. However, the Spark Beetle only activates its shield in short periods, leaving itself open and vulnerable when the shield switches off.
In Sonic Adventure 2, the Spark Beetle's shield is shown to be somewhat ineffective, as the player can use Tails' and Robotnik's walkers to outflank it. Even with the shield up or not, simply using missiles and laser cannons to lock-on and fire at a Spark Beetle will destroy it. The shield also proves to be powerless against Sonic's and Shadow's Light Speed Attack, which cuts right through the shield and pulverizes the defenseless robot inside.
In Shadow the Hedgehog, a Spark Beetle's shield can protect it from gunfire as well as regular attacks. Also in this game, the shields are electrical rings instead of the spherical shaped shields seen in Sonic Adventure 2.