From Worms Knowledge Base
This one is pretty much like the Anvil.
When the bowling ball stops bouncing, it then begins rolling down whatever slope it might find itself on, jumping over lumps in the terrain and rolling up opposite slopes with momentum. Whenever it comes into contact with a worm, the worm is squashed flat and takes a specific amount of damage, or is 'fire punched' out of the way, with damage proportional to the speed of impact.
When it finally comes to rest, it remains on the terrain, still capable of rolling around and damaging worms if the terrain beneath it is shot. It may also be knocked around by explosions from weapons.
The potential for bugs and flaws in programming this weapon is enormous. The ability of this weapon to roll is unique to Worms. Even on the steepest terrains, weapons that look as though they should roll down, like the grenade or cluster bomb, can remain static. This is because the centre of mass of the object is irrelevant, it is always positioned above the contact surface between grenade and land, preventing it from having a moment-effect on the object.
So this weapon would require new physics. The centre of mass would have to be checked every so often, and if it lies in the right place when the weapon sits on a slope, the weapons moves in the direction of the slope. Momentum would also play a key part if the Bowling Ball was to be able to roll up slopes.
The landscapes on Worms are often jagged, pointy and generally hard to navigate, so it wouldn't be often that you find a nice big slope with enemy worms on to flatten with the Bowling Ball. But still, this weapon has great strategic potential. Rolling it down neatly blowtorched tunnels is sure to be fun, and bouncing it down a twisty canyon without a fuse time to worry about will ensure that the worms at the bottom are not safe.
A Bowling Ball would seem to fit perfectly into the Worms series. With a cheesy "bowling alley strike" sound effect to accompany the 'fire-punch' contact between worm and Ball, and worms squashed flat before popping up again, it's the perfect choice for a comical addition to the weapons menu. It also opens up a window for impressive and fluky shots, such as rolling it down towards a 'ski-jump' and hitting a worm on the other side of a pit. Rolling it off a cliff and striking a worm anvil-style is another possibility sure to get laughs.