I made these after seeing Saber-Scorpions' Left 4 Dead survivors, because I was shocked he didn't make special infected :O
The Hunter. It's agile, fast, strong, can jump great distances and pounce survivors leaving them helpless, unless team mates help, and it's extremely weak. Its WIP, I may use Han's hood in the new Hoth Battle set. (sorry for the blurry pic)
The Smoker is a unique infected, having a long tongue to separate survivors.
This was the first 100% complete infected, and I liked the way he turned out. (sorry again for the blurry pic)
The Witch, a very agitating infected that can slice you in two if disturbed from her never ending crying.
The Boomer is a clumsy, disturbing fellow, he vomits on survivors, attracting hordes like a shark to blood. Explodes in death, bile on the survivors works just as well as vomit.
The Tank is the largest and the most dangerous of all, and packs a punch! It's best for survivors to work together, but just don't stay to close together when chased by this infected.
Here's a special guest! The Charger, an assumed half-infected-half-tank infected. He isn't in Left 4 Dead, but appears in Left 4 Dead 2.
I may or may not make the Spitter, considering it's design is a WIP for the game. Thank god.