"If you men will take no pay.... then none of us will."
The scene where the 54th is cheered as they head out for the assault on Fort Wagner is one that makes the audience want to stand up and cheer along with them.
The entire assault on Battery Wagner (Fort Wagner in the movie), but particularly the final charge. After getting absolutely hammered by artillery for almost half a day, the 54th manage goes on a Roaring Rampage of Revenge after Shaw's killed. They overran the parapet and partially occupy the fort, before they are finally beaten back (off-camera) by the fort's internal defenses.