Giant Anteaters are on 2 different episodes, and are #4 on Body Parts, and #9 on Big Mouths. They use their super long tongue for licking up ants and termites. Their tongue is a meter long, and is sticky. However, their mouth is only 2% of their body length.
If following the countdown of extreme Body Parts, the next contender is up for debate if it is a giant sucker.
If following the countdown of extreme Big Mouths, here is a link to the next contender, who has a special technique that allows it swallow something bigger than its head.