User:Troll
This should also be a reserved name as it is subject to identity dispute if anyone claims it or tries to use it.
One good use for it would be to make it available to any anonymous IP user to debate something with a logged-in user. This would assure both parties they were talking consistently with one person, and, it would be possible for the Consumerium Governance Organization to easily monitor all debates with so-called trolls (they would just have to look at contributions of this account). When the debate is over, the account is formally surrendered so that another troll may use it.
See also User:Sysop, User:Administrator, User:Boss, User:Mediator (and history of this account on Wikipedia, User:Arbitrator, User:Lowest Troll and User:Lowly Troll (and variants User:Low Troll, User:LowestTroll, User:LowlyTroll). Any potentially priveleged or apparently priveleged name should be reserved.