This is a list I am making as I go through my Art History course for no particular reason so... Criteria is mostly aesthetic to be honest, although some are pieces I like for more contextual/historical reasons.

• Ishtar Gate (Mesopotamian)
• works of the Amarna period (Egyptian)
• mask of Agammemnon (Mycenean)
• Epigonos' Dying Gaul and Wife (Greek)
• Praxiteles' Aphrodite of Knidos (Greek)
• Nike of Samothrace (Greek)
• Barberini Faun (Greek)
• Erecetheion on the Athenian Acropolis (Greek)
• Altar of Zeus at Pergamon (Greek - Hellenistic)
• Portrait of a Flavian Woman (Roman)
• Ludovisi Sarcophagus (Late Roman)
• Pantheon (Roman)
• Hagia Sophia (Byzantine)
• San Vitale (Byzantine)
• St. Marks, Venice (Byzantine)
• basically all Byzantine mosaics
• Alhambra Palaces (Islamic)
• basically all Islamic designs
• Hiberno-Saxon illuminated manuscripts (Early Northern Medieval)
• Bayeux Tapestry (Romanesque)
• Notre Dame at Amiens (Gothic)
• Notre Dame at Reims (Gothic)
• Saint-Chapelle (Gothic)
• Orvieto Cathedral (Gothic)
• the North portal of Chartres cathedral (Gothic)
• Annunciation, Martini (Late Medieval)
• Birth of Venus, Botticelli (Renaissance)
• Primavera, Botticelli (Renaissance)
• Adoration of the Magi, da Fabriano (International/Renaissance)
• Garden of Earthly Delights, Hieronymus Bosch (Northern Renaissance)
• Isenheim Altarpiece, Grunewald (Northern Renaissance)
• Michelangelo's David (High Renaissance)
• Michelangelo's everything (High Renaissance)
• Venus, Cupid, Folly, and Time, Bronzino (Mannerism)
• Palazzo del Te, Romano (Mannerism)
• Venus of Urbino, Titian (Venetian Renaissance)
• Isabella d'Este, Titian (Venetian Renaissance)
• Judith and Holofernes, Artemisia Gentileschi (Baroque)
• Gentileschi's everything (Baroque)
• Burial of Count Orgaz and everything else, El Greco (transitional Mannerist/Baroque)
• Ecstasy of St. Teresa and everything else, Bernini (Baroque)
• San Carlo, Borromini (Baroque)
• Vermeer's everything (Northern Baroque)
• various still lifes, Rachel Ruysch (Northern Baroque)
• vanitas paintings, van Oosterwyck (Northern Baroque)
• Return to Cythera, Watteau (Rococo)
• Hogarth's everything (18th Century)
• Grand Odalisque, Ingres (Neoclassicism)
• Coronation of Napoleon, David (Neoclassicism)

GENERAL NOTE ... at this point it becomes mostly a list of artists I like, with a few specific pieces

• Goya (Romanticism)
• Gericault, particularly Raft of Medusa (Romanticism)
• Delacroix, particularly Chopin portrait (Romanticism)
• Turner (Romanticism)
• Friedrich (Romanticism)
• Garnier's Paris Opera (Romanticism)
• Nash's Royal Pavilion in Brighton (Romanticism)
• Courbert (Realism)
• Millet (Realism)
• Manet, particularly Olympia (Realism)
• Sargent (Realism)
• Millais (Pre-Raphaelite)
• Rossetti(Pre-Raphaelite)
• ALL THE IMPRESSIONISTS (Monet, Morisot, Degas, Cassatt, Renoir)
• ALL THE POST-IMPRESSIONISTS (Seurat, Toulouse-Lautrec, Van Gogh, Cezanne)
• Rodin
• Picasso
• Braque
• Klimt
• Schiele
• Matisse
• Kirchner
• Beckmann
• Kandinsky
• Malevich
• Duchamp
• Rietveld
• Mondrian
• Magritte
• Frida Kahlo
• Diego Rivera
• Hopper
• Pollock
• de Kooning
• Rothko