Accomplish the indicated achievement to get the corresponding number of 
Gamerscore points:

  Let's Get Punchy (15 points): Melee 5 soldiers. 
  Bomba Punter (20 points): Punt 20 Bombas. 
  My Head A-Splode (20 points): Get 50 head shots. 
  Make 'Em Scream (20 points): Get 100 soldiers to scream. 
  To Kill a Blackbird (15 points): Destroy the helicopter attacking the Vice 
  President. 
  Look Out! (5 points): Kill a soldier with a Bomba. 
  Walkin' on Water (5 points): Make it from one end of lake to the other in 
  hyper-Speed. 
  Hero (50 points): Complete the game on any difficulty setting. 
  Completionist (20 points): Complete the game with 100% of the items. 
  Minimalist (10 points): Complete the game with less than 13% of the items. 
  Proven Grounds (10 points): Complete the Proving Grounds. 
  Serious Complex (10 points): Level-up to experience level 50.