What trophy does Beowulf display in Heorot after defeating Grendel?

Beowulf displays Grendel's arm in Heorot after defeating the monster.

Grendel has terrorized King Hrothgar's Danish hall for twelve years, attacking the sleeping warriors at night. Beowulf refuses to use weapons because Grendel is protected against ordinary blades, so he grapples with the creature using his extraordinary strength. The struggle ends when Beowulf tears off Grendel's shoulder and arm.

Grendel escapes to his mere and dies from the wound. In the morning, Beowulf and the Danes bring the severed limb back to Heorot, where it is hung up as proof of the victory. The poem emphasizes the whole shoulder and arm, including Grendel's powerful grasp.

The head is also associated with Beowulf's victory, but it belongs to the later episode involving Grendel's mother. After killing her underwater, Beowulf finds Grendel's corpse and brings its head to Hrothgar. The sword, meanwhile, is a weapon used in that later underwater fight.