Mitosis

When activated, the worm using this weapon performs mitosis, and splits cleanly into two worms. Health is halved, such that each clone have the same amount. This weapon does not end the turn for the original worm, who can continue as usual. Another possible feature of this weapon is to have both clones share the damage that either of them recieve, as if they were one worm still, but in two places at once. (Schrodinger's Cat, anyone?)

As with the Reinforcement Worm, this weapon would have to be in limited quantity, otherwise a player could keep cloning worms without a thought for his processor. Either the weapon itself could be limited, or the numbers of worms on the terrain should be limited (so that the weapon is disabled at a certain number)

If the worm happens to be in a tight spot where another worm simply could not exist without intersecting terrain somehow, then the clone should take the same position as the original worm, in the same way that worms generally overlap during games anyway.

If one worm was to die, nothing significant should happen, despite sharing of damage. The remaining worm would carry on as usual.

Finally, the cloned worm will need a name. This could just be exactly the same; Worms can cope with identical names. Or it could add "2" or "clone" on the end, but this may exceed the character limit.

This weapon would be useful in those situations where you don't want to risk a (whole) worm, and splitting a powerful worm will give you a sort of back-up copy should things go horribly wrong. You may even want to use a kamikaze or suicide move without actually killing your worm, particularly useful on low health. Even better, doubling the number of worms will double the damage you can do in a suicide move, if you plan on killing both with a standard weapon, near an enemy worm.

Also useful for restricted maps where select worm is available (e.g. "Team17" games), as it enables you to position more worms around the map for greater coverage and strategical freedom. Without select worm though, this weapon could turn out to be more a hinderance.

Cloning is one of those other controversial topical subjects of the modern world, so bringing that into Worms with a comical, over-simplified animation would be welcome, and it could be accompanied by that 'blub' sound-effect you're most likely to associate with a blob of microscopic jelly falling down the stairs.