How'd You Do That?-30 GS: Kill a Brute Cheiftain with a Plasma Pistol, with no help, or any other shots or melees added Ninja-10 GS: Assassinate a Brute Cheiftain before he activates his Invincibility ODSTs Can Be Spartans Too-50 GS: Survive 15 (or 10) rounds in a row in Firefight on Legendary mode with just one player and without dying Extermination Was So Last Season-40 GS: Get four Killonaires (one in each round, and the rounds are in a row) of Firefight These seem like real achievments that would be in the game. [Edited on 06.17.2009 10:26 PM PDT]