30 Kills: SAS - 12 Trophy in Uncharted 3: Drake's Deception

The SAS - 12 is the best shotgun in the game and although it's no good at a distance, up close and personal it can't be beaten. You first get this weapon in Yemen in Chapter 10 - Historical Research but you don't really have a chance to use it until later on. Here are a couple of good farming spots:

Chapter 16 - One Shot at This

Both of your opportunities come on this Chapter. Your first place to earn this is in the same spot as you can get the 4 kills with one grenade after dropping through the skylight. The guy down here carries a SAS - 12 and after you shoot the locks to let Elena in and the jeep turns up (the one you get Dyno-Might Master on) you can slip into cover and blow a good 5 guys away before you can restart the checkpoint and farm some more.

The other good area is just past this. Once the cutscene of Drake accidentally letting the jeep fall out of his grip and crash through the gates, take out the 3 guys that stand around looking. One has a SAS - 12 so grab it and head into the next area. Now simply run around and shoot as many goons as you can, you will run out of ammo before you run out of enemies so spend the full mag and restart the checkpoint and go again until you have all 30 kills.