A hover cannon. Hover cannons functioned as heavily-armed, floating assassin droids. These droids utilized powerful repulsors, giving them the capability to ascend to the Senate Landing Platforms located on Coruscant. In 32 BBY, a group of these cannons were deployed by Coruscant mercenaries in an attack targeting Queen Padmé Amidala and Captain Quarsh Panaka while they were en route to 500 Republica.
The hover cannons are featured in the 1999 video game adaptation, Star Wars: Episode I The Phantom Menace video game. The mission they are part of directly clashes with the events shown in the movie, Star Wars: Episode I The Phantom Menace. Specifically, the film depicts Amidala arriving at the Senate Building without being attacked.