Boomer

 Boomer is a virus from Mega Man Battle Network 3. It attacks by shooting a boomerang that travels along the walls of the field. It hits every panel except for those in the middle.

Boomer
 Boomer is a black and purple variant with red eyes and a silver blade.

Gloomer
 Gloomer is a green and blue variant with orange eyes and a silver blade.

Doomer
 Doomer is a purple and green variant with yellow eyes and a gold blade.

BoomerΩ
 BoomerΩ is a blue and light-blue variant with orange eyes and a silver blade.