Rhino

This is released like a single Mad Cow. In fact, it acts just like a Mad Cow, exploding when it hits a wall. But rather than exploding when it hits a worm, it simply nudges that worm forward, like a Prod. It keeps nudging until it hits the wall and explodes.

Given that it works mostly just like a Mad Cow only with an extra prodding feature, this should not be at all hard to program.

This could be useful for piling up several worms if, say, they are all lined up on a bridge or a slope; whereas a Cow would explode on contact with the first worm, and all following Cows would fall down the hole.

The more animals the better. Although very similar to the Mad Cow, the small difference it has makes it unique enough, and able enough to cope with situations that other weapons wouldn't, to be in the game.