Young Justice, the animated series about D.C. comic book sidekicks getting their own covert Junior Justice League, had a throw-away Beowulf reference in episode 19, “Secrets.”
In that episode, a villain named “Harm” (who obnoxiously always referred to himself in the 3rd person) steals Beowulf’s sword, which can only be wielded by the pure of heart — and as his heart is pure evil, it counts. Once he has learned the incantation to make the sword work (which is vaguely-Old-English sounding gibberish), he uses it to wreak a bit of havoc.
Beyond that, it isn’t really clear what sword this is supposed to be, since in the Old English poem Beowulf fights Grendel unarmed (heh heh), and in the battle with Grendel’s mother Unferth’s sword Hrunting fails, and the Beowulf has to kill her with a giant sword she happens to have lying around her lair.
One cool potential reference to Grendel, though — the sword is actually sheathed in what looks like a mummified arm. Not exactly canonical to the medieval poem, but cool nonetheless.
