There are a huge number of Gods, Titans, and other figures to name, so let me suffice by putting together a list of the 'major' Gods, Titans, and Heroes, and referring you to Wikipedia and/or theoi.com for the rest.


Protogenoi
  • Aether (Αἰθήρ, Aithḗr,'Light')
  • Ananke (Ἀνάγκη, Anánkē, 'Fate' or 'Compulsion')
  • Erebos (Ἔρεβος, Érebos, 'Darkness')
  • Eros (Ἔρως, Eros, 'Desire' or 'Love')
  • Gaea (Γαῖα, Gaîa, 'Earth')
  • Hemera (Ἡμέρα, Hēméra, 'Day')
  • Hydros (Ὑδρος, Hydros, 'Primordial Waters')
  • Hypnos (Ὕπνος, Hypnos, 'Sleep')
  • Khaos (χάος, Cháos, 'Chaos' or 'Air')
  • Khronos (Χρόνος, Chrónos, 'Time')
  • Nêsoi (Νησοι, Nē̂soi, 'Islands')
  • Nyx (Νύξ, Nýx, 'Night')
  • Ôkeanos (Ωκεανος, 'Water')
  • Ouranos (Οὐρανός, Ouranós, 'Sky')
  • Ourea (Oὔρεα, Oúrea, 'Mountains')
  • Phanes (Φάνης, Phánēs, 'Procreation')
  • Pontos (Πόντος, Póntus, 'Sea')
  • Phusis (φύσις, 'Nature')
  • Tartaros (Τάρταρος, Tártaros)
  • Thalassa (Θάλασσα, Thálassa, 'Sea')
  • Thanatos (Θάνατος, Thánatos, 'Death')
  • Thesis (Θεσις, Thesis, 'Creation')
Uranides
  • Atlas (Ατλας, God of astronomy and navigation)
  • Epimetheus (Επιμηθευς, God of afterthought)
  • Hyperion (Ὑπεριων, God of Light)
  • Iapetos (Ιαπετος, God of the mortal life-span)
  • Koios (Κοιος, God of the inquisitive mind)
  • Krios (Κριως, God of the constellations)
  • Kronus (Κρονος, who rules of time and the ages)
  • Okeanos (Ωκεανος, God of the great earth-encircling river Okeanos, the font of all the earth's fresh-water)
  • Phoebe (Φοιβη, Goddess of intellect)
  • Prometheus (Προμηθευς, God of forethought and crafty counsel)
  • Rhea (Ρεα, Goddess of female fertility and the wild mountains)
  • Tethys (Τηθυς, Goddess of nursing and of the underground sources of fresh-water)
  • Theia (Θεια, Goddess of sight and precious gemstones)
  • Themis (Θεμις, Goddess of natural order, divine law and tradition)
  • Menoitios (Μενοιτιος, God of violent anger and rash action)
  • Mnemosyne (Μνημοσυνη, Goddess of memory, words and language)
Titanes
  • Ankhialê (Αγχιαλη, Goddess of the warming heat of fire)
  • Asteria (Αστερια,Ggoddess of the oracles and prophecies of night)
  • Astraios (Αστραιος, God of the stars and planets, and the art of astrology)
  • Aura (Αυρα, Goddess of the breeze and the fresh, cool air of early morning)
  • Klymenê (Κλυμηνη, goddess of renown, fame and infamy)
  • Diônê (Διωνη, Goddess of the oracle of Dodona)
  • Êôs (Ηως, Goddess of dawn)
  • Eurybia (Ευρυβια, Goddess of the mastery of the seas)
  • Eurynomê (Ευρυνομη, Goddess of water-meadows and pasturelands)
  • Helios (Ἡλιος, God of the sun, oaths and sight)
  • Hekatê (Ἑκατη, goddess of (the protection against) magic, witchcraft, the night, moon, ghosts and necromancy)
  • Lêlantos (Ληλαντος, God of air and stalking prey)
  • Lêtô (Λητω, Goddess of motherhood and protectress of the young)
  • Melisseus (Μελισσευς, God of honey)
  • Mêtis (Μητις, Goddess of good counsel, advise, planning, cunning, craftiness and wisdom)
  • The (Elder) Mousai (Μουσαι, Goddesses of music)
  • Pallas (Παλλας, God of warcraft and the Greek campaign season of late spring and early summer)
  • Persaios (Περσαιος, God of destruction)
  • Phorkys (Φορκυς, God who presides over the hidden dangers of the deep sea)
  • Selênê (Σεληνη, Goddess of the moon)
  • Styx (Στυξ, Goddess of the Underworld River Styx and of hatred)
Olympic Gods
  • Aphrodite (Ἀφροδίτη, Aphroditē)
  • Apollo (Ἀπόλλων, Apóllōn)
  • Ares (Ἄρης, Árēs)
  • Artemis (Ἄρτεμις, Ártemis)
  • Athena (Ἀθηνᾶ, Athēnâ)
  • Demeter (Δημήτηρ, Dēmētēr)
  • Dionysus (Διόνυσος, Diónysos)
  • Hades (ᾍδης, Hádēs) / Pluton (Πλούτων, Ploutōn)
  • Hephaestus (Ἥφαιστος, Hḗphaistos)
  • Hera (Ἥρα, Hḗra)
  • Hermes (Ἑρμῆς, Hērmēs)
  • Hestia (Ἑστία, Hestía)
  • Poseidon (Ποσειδῶν, Poseidōn) 
  • Zeus (Ζεύς, Zeus) 
Heroes/deified mortals
  • Achilles (Ἀχιλλεύς, hero of the Trojan War)
  • Andromeda (Ἀνδρομέδα, Androméda, wife of Perseus)
  • Ariadne (Αριάδνη, a Cretan princess, wife of Dionysus)
  • Asklepios (Ἀσκληπιός, Thessalian physician made God of Healing)
  • Atalanta (Ἀταλάντη, Atalantē, slayer of the Kalydonian Boar)
  • Bellerophon (Βελλεροφῶν, hero who rode Pegasos)
  • Daedalos (Δαίδαλος, skillful craftsman and artist, father of Íkaros (Ἴκαρος))
  • The Dioscuri (Διόσκουροι, divine twins: Kastor (Κάστωρ) and Polydeukes (Πολυδεύκης))
  • Ganymede (Γανυμήδης, cup-bearer of the Gods)
  • Herakles (Ἡρακλῆς, ascended hero)
  • Jason (Ἰάσων, Iásōn, leader of the Argonautai (Ἀργοναῦται))
  • Odysseus (Ὀδυσσεύς, hero of the Odysseia)
  • Orpheus (Ὀρφεύς, legendary musician, poet, and prophet)
  • Perseus (Περσεύς, first of the heroes of Hellenic mythology)
  • Psyche (Ψυχή, Goddess of the Soul)
  • Theseus (Θησεύς, founder-king of Athens)