You can get a "Hairy Tongue..."

Via Reddit

This is real. No Photoshop. This man has hair on his tongue..

Basically this is called "Black Hairy Tongue", there are a few causes for this...

Causes:

Poor oral hygiene
Smoking tobacco
Drinking a lot of coffee or tea
Using antibiotics (which may disrupt the normal balance of bacteria in the mouth)
Being dehydrated
Taking medications that contain the chemical bismuth (such as Pepto-Bismol for upset stomach)
Not producing enough saliva
Regularly using mouthwash that contains peroxide, witch hazel, or menthol
Getting radiation therapy to the head and neck