Jurassic The Hunted

You will rack up 1-shot-kills normally through out the course of the game, but it becomes easier once you obtained the shotgun on Level 3 Sinking Feeling. Press the LB button for slowmo/adrenaline rush mode and aim for the head. You can replay levels where you feel most comfortable to rack up more points, I recommend playing level 3 over and over if you don't get it by the end of the game. NOTE: you must finish the level for your stats to save(if you didn't get enough kills)

Edit: 07/22/2011 According to member LausDomini Level 10 is a good grinding level too.