Depends on what you mean by that. Do you mean ‘unique’ in the sense that you can only get them from pwning specific forums? If so, a few of those already exist. Ophelia’s Bad Poetry from finishing her quest; the Mouse Fraggingrites (or however the hell you spell it) gives you for friending him Or do you mean items that only one person ever can own, and when a forum gets re-pwned, it goes to the new pwner?

Because in the latter case, I think that would be horrible – with how quickly forums get repwned, you’d get that special thing maybe long enough to get a screenshot.