•Why it earns a slot
Beowulf is the longest surviving Old English poem and the foundational text of English literature, preserving a Germanic heroic world of hall-culture, comitatus loyalty, and fate-haunted courage while layering Christian commentary onto pagan legend.
Beowulf, a mighty Geatish warrior, crosses the sea to aid the Danish king Hrothgar, whose great mead-hall Heorot has been terrorized for twelve years by the monster Grendel. After killing Grendel and then Grendel's vengeful mother in her underwater lair, Beowulf returns home in glory, eventually becomes king of the Geats, and rules for fifty years until a dragon, roused by a stolen cup, forces one final battle that costs him his life.
This distillation is written from the freely available original, which is always the better read when you have the time: gutenberg.org.