Exaggerated prehensile tongues are a common literary device for RPGs and Science Fiction or Fantasy but they actually do exist, even in humans.
Human infants grasp the breast with their tongue when suckling in order to lift and compress the ducts beneath the areola between their tongue and the roof of their mouth. This movement, along with the suction created by sealing the lips (lips are also prehensile) and dropping the jaw expresses the milk. This instinctive skill diminishes as infants grow and suckling transitions to the more adult form of sucking (as on a straw).
Human lips remain prehensile (just watch a random movie goer with full hands grasp a bit of popcorn with his lips). Some people also have the genetic trait that allows them to roll their tongue into a cylinder; granting some degree of prehension, especially when combined with suction.
Other animals have prehensile tongues and use them for various tasks.
Giraffes are probably the creatures best known for having a prehensile tongue. It is fairly dramatic, 18 inches long, and black (reduces sunburn). Giraffes use it to pluck leaves from tall trees. Less known but still having varying degrees of similar tongue prehension are okapi, cows, goats, buffalo, moose and antelope. All these grazing animals use their tongue to grasp foliage and pull it into their mouths.
Many lizards and frogs use their tongue as a hunting tool, combining the stickiness of the wet surface with interlocking papillae, which grasp irregular surfaces on the prey. The inefficiency of these mechanisms limit the size of prey they can capture.
Chameleons use a suction cup like transformation of their tongue to capture larger prey. After darting out, their tongue forms up into a pouch, which engulfs the head of larger prey or the whole body of smaller victims. The pouch rolls inward like a conveyer belt, holding the prey tightly and allowing the capture of animals as large as other lizards or small birds. Most lizards are not specialized in their feeding behaviors but there are two ant-eating lizards that flick or rotate their tongue to capture and transport the prey into their gullet.
Elephants can lift a segment of the tongue to drape over a morsel of food as small as a peanut placed on it then ripple it backwards into the mouth with a wave like motion.
UPDATE
hmmm,
oolong has suggested hummingbirds and anteaters as examples - probably correct but not confirmed ...
SOURCES used outside of the previously acquired and unattributable trivia that fills my brain:
http://www.fhsu.edu/biology/ranpers/rm/details.htm
http://jan.ucc.nau.edu/~kiisa/pdfs/Herrel%20et%20al.%202000.pdf
http://jan.ucc.nau.edu/~kiisa/pdfs/Meyers%20and%20Herrel%202005.pdf
http://www.audubon.org/bird/BoA/F24_G1c.html
okapi by
zgirll - confirmed with a quick googling