From Worms Knowledge Base
Your worm pulls out a boomerang upon selection of this weapon, and when thrown not too differently to a grenade, it follows a looped path through the air. Any worms in the path of this boomerang are struck by it, and take a small amount of damage. What's unique about this weapon is that you can only ever have one, but it can be re-used again and again, providing that the boomerang returns safely to the worm from whence it came. The Boomerang is lost if it hits land or water, or an object such as a barrel.
The Boomerang is affected by wind, complicating its use but making it all the more special.
At first you may think that determining the flight path for this weapon would be quite complex, when it need not be at all. The path could be no more than a balloon-shaped bubble, which is distorted in the presence of wind, changes size with power applied, and changes direction with aim. That way, it does not matter how strong the wind is, the Boomerang will always return providing there are no obstacles. However, one problem caused by this is that is the worm moves during retreat time, the Boomerang's flight path may not intersect the worm, thus causing it to be lost. This could be rectified by disabling retreat time with the weapon, which is already built into the game (in the teleport).
If the boomerang hits land it should ideally be made to disappear, or bounce off and fall down into the water infront of the terrain, with a sharp 'stick-against-stick' sound effect. Any worms struck by the boomerang could be propelled slightly in a direction, to give the weapon more strategic potential, or just made to lose health and perform the stick-head-in-ground animation.
Because the weapon can only exist or not exist, rather than have a quantity, and can be re-used, new programming for the weapon would have to be made. Whether that would be simple or not I cannot begin to speculate about. The boomerang, if lost, should be retrievable if found in a crate, but any such find if a boomerang is already in possession would simply go to waste.
The fact that this weapon can be used again and again puts it in the same league as standard infinite weapons such as grenade and bazooka. But those weapons are so much more versatile, so any incentive for using the boomerang would have to come purely from the damage it can deal. Once a suitable value is in place, it is up to the player to use the boomerang carefully so as not to lose the precious weapon. The problem here is that it would have to do a lot of damage to be worth using, but this opens up the possibility of 'abuse' where the player can use the boomerang at zero range and guarantee a hit, in a similar way that the minigun can be 'abused' with close-range use.
Aesthetically, the boomerang is another one of those innocent-looking-toy-turned-deadly-weapon objects, all of which are welcome in the cartoon environment of worms. Animation for this weapon would be unexciting at best, but an australian-looking hat worn by the worm is a must.