A Special Infected called "The Leaker" was being developed. It had similar attacks as the Spitter and Boomer, and the ability to plant itself in the ground and act as a mine bomb. It was removed because the Survivors could run away from it, as the Leaker would alert the Survivors that it was planting itself.

However, it is still possible to play as The Leaker with console commands by using "Map MAPNAME Versus", then typing in console "Boomer_Leaker_Chance" and a number between 0 and 1. You will know when you are a leaker if it says "You are a/the Leaker!", or you explode on death and cause a small fire.