Perfect example of a well thought out F2P game is League of Legends. While you can put money into it if you wish, doing so does not give you any gameplay advantage over the people that don't spend a cent. The only things that can be bought with real money are things like characters (which can also be purchased using the in-game monetary called IP which is earned through experience) and skins to make your characters look different. Any actual gameplay upgrades like armour etc that can give you an advantage over your opponents can only be purchased via the IP system which you have to earn rather than simply buy. This is why it's become so popular so fast, I just don't understand why more F2P games aren't like this.
Ballen04's comments