The Lone Gunslinger is the central antagonist of Ice Age 2: The Meltdown.
Role in the film
The Lone Gunslinger acts as the voice who warns the other animals of the dangers coming soon due to the valley where they reside flooding up with water. The Lone Gunslinger only warns them of the danger and little else, rather hoping that one or two of the animals leaving will die, furnishing food for he and the other vultures which he is presumably family and friends with.
As he watches all of the creatures in the valley leave to safety, he makes snide and opprobrious remarks with his friends about it, and this escalades to the point of singing a musical number on how much they plotted to eat the other animals.
He and the other vultures sang the altered version of Food Glorious Food. This song can be herd on the Ice Age 2 scores album. The Lone Gunslinger was last shown flying over the "boat" full of escaping animals and making snide and opprobrious remarks. "Do not leave your children unattended. All unattended children will be eaten."
In the storybook version, he and his fellow vultures were shown to have ended up feasting on the two dangerous sea reptiles named Cretaceous and Malestrom.
Also, the Gunslinger is usually seen with another, higher voiced vulture. Because of his/her voice, it is unsure whether he/she is his wife/girlfriend, or his best friend.