The soldier in the opening sequence. He knows he is going to die but he fights as hard as he can to use his last few seconds of life to set off the Great Wall's warning-torch-system, and then stands up to the scary Shan Yu before his death. Thanks to him, Shan Yu fails. Without his warning, the Huns' entry into China would have gone unnoticed, and the entire country would have likely fallen to invasion due to being completely unprepared for war.
Soldier to Shan Yu: Now all of China knows you're here.