Duckers are a kind of mobile cannon that walks along the terrain, top or bottom, on two stilt-like mechanical legs. They appear from the left side of the screen, race along the terrain in order to get ahead of the Vic Viper, and fire back at it. They usually shoot a single basic bullet, but on other games/loops/difficulties, a Ducker may shoot more the one. Duckers have made appearances in nearly every Gradius game, as well as others. They are usually found in the first stages, and then later stages where many mechanical enemies attack.
Usually two Duckers will run on screen together, one on the top, one on the bottom, far ahead of the Vic Viper, then stop and fire bullets at it. They will continue running if Vic Viper passes them until they are ahead again, and the pattern repeats.
- Duckers sometimes do very weird things in the games, most notably in Gradius. In the last level, when they try to change elevations, instead their sprite simply moves extremely fast to the required elevation.
- Two enemies in Contra III: The Alien Wars (also by Konami) are inspired on this enemy: the Rotating Ducker and the Tetranducker (the later also being inspired in part on the Tetran).
- In the game Monster Maulers, an older-looking steampunk version of the Ducker is piloted by the first of the game's three bosses, Mr. Chin.
- Duckers also appeared in other Konami franchises, such as Yu-Gi-Oh!.