Gears of War 2

Here is a list of the weapons you need to complete this achievement all you need to do is get one kill with each weapon,

Shotgun,
Frag grenade,
Lancer,
Boomshot,
Scorcher,
Longshot,
Ink grenade,
Torque bow,
Mulcher,
Mortor,
Hammer of dawn,
Gorgon pistol,
Boltok pistol,
Cog pistol,
Hammerburst.

An easy way to achieve this would be to set up a private game vs. a friend/bot/second controller then customise all the weapons for the ones you need and get your kill with it.

For this achievement you need to kill an enemy with each of the weapons in the game.

Here's a list of the weapons you need to get a kill with so that you can mark them off as you get a kill with them;
• Boltok Pistol
• Boomshot
• COG Pistol
• Frag Grenade
• Gorgon Pistol
• Hammer Of Dawn
• Hammerburst
• Ink Grenade
• Lancer
• Longshot
• Mortar
• Mulcher
• Scorcher
• Shotgun
• Torque Bow

Now the achievement is left entirely open as this can be obtained by playing a match in any mode, so while you have the option of playing online in a ranked/social match and working toward this achievement casually you can also choose to get this achievement out the way by playing a local game with 2 controllers.

The quickest way to get this achievement is to set up a local game, set the game type to Warzone, set the round limit to 1 and work your way through the maps while killing the second player, this way you have absolutely no threat to contend with as the second player won't do anything unless you make it.

You can use this method any way that you want, you can set up a match with you facing off against a team of bots if you want, it's entirely up to you, I've just outlined the easiest and fastest method that I know of.