Guild Wars 2

First per the rules of conduct for Guild War 2

1. While playing Guild Wars 2, you must respect the rights of others and their rights to play and enjoy the Game. To this end, you may not defraud, harass , threaten, embarrass or cause distress and/or unwanted attention to other players. This includes posting insulting, offensive, or abusive comments about players, repeatedly sending unwanted messages, reporting players maliciously, attacking a player based on race, sexual orientation, religion, heritage, etc. Hate speech is not tolerated.

Now I know there is a lot of Blizzard references in this but it is good for any MMO. Please read and use if you feel you have or are being harassed.

http://www.applecidermage.com/2012/03/07/internet-harassment-and-you-a-guide/