Arterra

What actually MAKES a good username?
Sure, originality is in the equation somewhere, but lets face it: the larger the audience, the more awesome usernames are already taken. Relevant to the website/game? You can only go so far before it just blends in as a fanboy glance-over.
The truth is that a username is just that, a name. A name is nothing but a abstract marker, or put simply, the way you represent yourself. People usually think that means that the username defines the person, but you really have to face reality; a username is only as good as the user.
Are YOU a helpful poster? DID you farm all the gear you could? Unless you can nab a username that has a awesome face-value, like Obamanation or Terminator (derp juxtaposition) the username itself means nothing, it is your ACTIONS that give it meaning, and worth.
To be honest, even with a name like Ender if you act immature, you will be perceived as such. Why do you think people freaked out when they think their usernames might be taken? Are they all really that good/original? Usually not. It is that they have invested their personality and reputation into it, and do not wish to be perceived as they are not by a imitation.
[common example: the SL beta and the 50 plat reserve-a-name angst]

So, having a creative block at a new site? Dont sweat it! Any name you pick will be the best it can be, as long as you are the best you can be. (well, with the exception of Buttz)