In some levels in the Instincts story, you can find a magazine named "Gamer Lamer". The magazine's cover has a mock-up picture of Gordan Freeman from Half-Life and the cover of the magazine reads "Quarter-Life 2 Amazing New Screenshots! Medal Of Shame, and Broom 3". These are mockups of popular games, which are Half-Life, Medal Of Honor, and Doom 3.
To unlock the following achievements, simply start a multiplayer game for each of the respective modes with a one minute time limit. Also, be sure to play it by yourself:
Multiplayer Master Predator Winner Seek n Secure Winner Steal the Sample Winner Team Chaos Winner Chaos Winner
To easily earn the Chaos Champion and Team Chaos Champion achievements, create a multiplayer game and set it up as Chaos (or Team Chaos). Set the round for one minute and auto launch for 15 seconds. Set the max number of players to 2 and private slots to 2. You will be in a continuous game by yourself. Allow the game to idle in this state to earn the achievements.