Abrahamic mythology
See also: Christian mythology, Islamic mythology and Jewish mythology

Anakim (Old Testament)

Gog and Magog

Goliath (Book of Samuel)

Nephilim

Nimrod (Old Testament)

Og (Book of Numbers)

Rephaite

Celtic mythology

See also: Celtic mythology

Cawr

Cormoran (Cornwall)

Fachen

Fomorians:

Balor

Banba

Bres

Buarainech

Cethlenn

Corb

Elatha

Ériu

Ethniu

Fódla

Tethra

Kaour

Greek and Roman mythology
See also: Greek mythology and Roman mythology

Argus Panoptes

Caca

Cacus

Cyclopes

Arges

Brontes

Polyphemus

Steropes

Epimetheus

Geryon

Gigantes:

Alcyoneus

Athos

Echion

Enceladus

Klytius

Hekatonkheires

Briareus

Gyges

Cottu

Menoetius

Talos

Titans:

Atlas

Coeus

Crius

Cronus

Dione (occasionally considered a Titan)

Gaia

Hyperion

Iapetus

Mnemosyne

Oceanus

Ophion (occasionally considered a Titan)

Phoebe

Prometheus

Rhea

Tethys

Theia

Themis

Hindu mythology
See also: Hindu mythology

Daityas

Hiranyaksha

Hiranyakashipu

Kumbhakarna

Mahabali

Ravana

Norse mythology
See also: Norse mythology

Bestla

Gorm

Jötunn

Ægir

Angrboða

Baugi

Bergelmir

Billingr

Bölþorn

Geirröd

Gilling

Gjálp and Greip

Gríðr

Gullveig (possibly)

Gymir

Hroðr

Hrungnir

Hymir

Járnsaxa

Kári

Loki

Alvaldi

Rindr

Skaði

Suttungr

Þjazi

Þrúðgelmir

Þrymr

Útgarða-Loki

Vafþrúðnir

Ymir/Aurgelmir

Other

Brobdingnag giant, from Jonathan Swift's Gulliver's Travels

Paul Bunyan (American folklore)

Ferragut (also known as Ferragus, Ferracutus, etc.)

Hurtaly (Og, Jewish mythology)

Gandareva

Gargantua and Pantagruel

Genie in-and-out giant spirit of the lamp. From Aladdin and His Wonderful Lamp, (re-written by Sir Richard Francis Burton) from One Thousand and One Nights or Arabian Nights

Gogmagog

John Henry (American folklore)

Iovan Iorgovan (Romanian mythology)

Jentilak or Gentiles: (Basque mythology)

Basajaun

Olentzero

Kapre (Philippine mythology)

Kroni (Ayyavazhi mythology)

Ojáncanu (Cantabrian mythology)

Ogias the Giant (Manichaean mythology)

Oni (Japanese folklore)

Si-Te-Cah (Paiute)

St Christopher (Roman Catholic)

‘Uj ibn Anaq (Islamic mythology)

Zipacna (Maya mythology)

Matsieng

Ellert and Brammert

Clickable links on Wiki:

http://en.wikipedia.org/wiki/List_of_giants_in_mythology_and_folklore