Also we have Cerberus Nasus :D
Nasus is Anubis in his basic skin (Egyptian Jackal/Human).
Ahri is an eastern myth (Nine-Tailed Fox).
Ao-Shin is another eastern myth (traditional Chinese dragon).
Soraka is a Satyr (Greek Goat/Human).
Alistar is a Minotaur (Greek Bull/Human).
Anivia is a Phoenix (Greek myth).
Olaf is a Viking and the embodiment of Thor (Norse God)
Hecarim is debatable (Greek Centaur, War-Horseman of the Apocalype, Headless Horseman)
Cassiopeia is Medusa and has a Siren Skin (Greek)
Amumu is a mummy (not sure where the myth comes from but based on Egyptian Mummification).
Little Knight Amumu references the myth of Excalibur
Maokai is a treant (not sure where that's from).
Rengar/Kha'zix (Modern Predator/Alien).
Nami is a mermaid (no real origin, just a sailors tail throughout the ages).
Galio is a gargoyle (Middle ages archetecture, gargoyles believed to keep evil spirits away).
Loch Ness Cho'Gath (Loch Ness monster obviously).
Many many christmas skins (Santa is a myth, sorry).
Jaximus is a reference to gladiators (Roman).
Pantheon and Myrmidon Pantheon reference Greek Myrmidon soldiers (not actually a myth)
Perseus Pantheon, the mythical hero Perseus (Greek).
Nunu references the myth of Yeti and Bigfoot/Sasquatch
Teemo is based on Satan (arguably a myth).
Many references to famous asian generals with skins for Jarvan, Xin, Tryn, etc.
Many champions were inspired by various myths throughout history, along with several skins too.
I want Baron Nashor to be a Hydra, where as he gets lower, he grows more heads and gets more powerful. It already kind of looks like that in the "Twist of Fate" video.