Wiglaf was the one Geat to stay with Beowulf in the battle with the dragon. He was a hero in that his loyalty his king never swayed. He approached the dragon while shouting encouragement to Beowulf, which distracted the dragon briefly. The dragon burned Wiglaf by over heating his shield so that Wiglaf was forced to take cover behind Beowulf.
When the dragon strikes Beowulf (after Beowulf's sword broke), Wiglaf used the opportunity to stab the beast in the belly, the only soft part of his body. That injured the dragon enough that Beowulf was then able to finish the task of killing the dragon.
Beowulf's wound, however, was a fatal one. Wiglaf stayed by Beowulf's side, brought him water, and showed him some of the dragon's treasure, but to no avail. Beowulf gave Wiglaf his armor and his authority, making the loyal Wiglaf the next king of the Geats.