Call of Duty 3

Here are some acheivements that can get you 100 Xbox Live Gamerscore Points:

Close Quarter Combatant - Complete a mission without firing a round. You can still use melee attacks and hand grenades.

Here are some acheivements that can get you 5 - 15 Xbox Live Gamerscore Points:

Basic Training (5) - Complete the basic training in the beginning of Saint Lo.5.
Purple Heart (5) - For perserverence despite grevious injuries.
Canadien Highlander (10) - Complete 2 missions as a Canadien Soilder.
Polish Tanker (15) - Complete 2 missions as a Polish Soilder
Battle Scavenger (15) - Complete a mission by firing only German weapons. Melee attacks DO NOT count.
Assault Trooper (15) - Complete a mission by firing only assault rifles. Melee attacks DO NOT count.
Supply Officer (15) - Supply ammunition to at least 20 friendly soldiers in a single ranked match. (Multiplayer only)
Rifleman (15) - Complete a mission by firing only bolt action rifles. Melee attacks DO NOT count.

Successfully complete the game to unlock interviews with veterans Gordon Boulton, Sgt. John D. "Bud" Hawk, and Sgt. Stan Markut.

Note: This trick only works when playing an online match. Find a game that is playing at Eder Dam online. Go to where all the sheds are located and the Allies regularly start CTF games. There will also be a jeep respawn and boxes out in front of the sheds. Go down to the edge of the map where there should be a broken bridge and more sheds. Take the motorcycle that is near a fence and the broken bridge. Get onto the motorcycle in the driver's side and drive up to the part of the shed on the left when facing down the hill. After that, drive into that open part of shed. Accelerate while turning into the top left corner. Following this, continue accelerating and turning, but while doing this exit the vehicle. If done correctly, you should have entered a see-through chamber which is not meant to be entered. You can see 360 degrees around and it should be clear. Note: There is also a window frame here, and if you walk up to it until you cannot continue further, you should be pointing the barrel of your gun out and can shoot at enemies walking by. They will not be able to see you through the solid outside. It is also recommended that you take in either a support or anti-armor class so that you can resupply yourself with ammo. You cannot exit the chamber. You must either respawn or kill yourself to exit This also works in many other nooks and corners in the online games, but only in the maps that have motorcycles in them.

If you particularly like a specific weapon from your faction, such as the M1 Garand or Bren, use the following trick to get more ammunition. Find a character on your team that is not an unkillable character (for example, Sgt. Dixon, or Lt. Robiechaud) and melee them. More often than not, the game will not fail the mission. Pick up the ammunition and continue the fight.