ANY MMOs with private servers -100% free
Oh, you mean without ^ this?
LOTRO (Lord of the Rings Online) and DDO (Dungeon&Dragons Online)
Both of these require either:
tons and TONS of $$ cash to purchase every bit of content
sub that give access to most content
OR
serious grind to get cash shop currency -TP (turbine points)
Yes, you can grind to purchase entire game if you want to do that (like year of grinding)
btw LOTRO and DDO are not “pure” F2P. instead they are “freemium”
http://www.webopedia.com/TERM/F/freemium.html