So, you seem to be thinking that it'll be hopeless to reach the high ranks. Let these features to reaching higher ranks be an incentive for you to contribute more!
You get this at 25 reputation.
For this, you will get a sexy green colored name, and you'll have been known as a contributor therefore you can view guide spoilers and such, and also use that chatbox.
You get this at 350 reputation.
For this, you will get an awesome blue name, and also gives you very important privileges. You will get access to the private board, the gaming and the general ones, where you can find invites to stuff, special hacks and guides, and more.
Edit: You now need a password that changes the first day of every month to have access to the Premium section.
Moderator rank. (Not really magenta colored)
You get this when appointed as a moderator and have Premium rank, you may become a mod before you reach premium, in that case, you will not receive the sexy MediumOrchid color until you become premium.
You get access to the Moderator board, and also a board where you can find posts automatically generated by a post reporter, when it will tell you information about the report and will tell you appointed moderators on the forums, and such.
This is achieved when you obtain 1000 reputation points.
You get an awesome violet-ish name and a great userbar AND lots of 'Woooooow :O'!
Thanks to Coldfire, Tracky and Hendricius for this amazing video.