30 Kills: G-MAL Trophy in Uncharted 3: Drake's Deception

The G-MAL is a very good rifle which is the equivalent of the old FAL of the previous games. It fires in bursts of 3 rounds and has a rifle scope to zoom in on far away enemies making it a superb weapon to use for headshots. You will first encounter the gun in Chapter 8 - Citadel and is a weapon you would do well to hang on to. There are a couple of good farming spots as follows:

Chapter 8 - Citadel

You will pick one up that's lying on a ledge just before the part where you stealth kill the enemies as mentioned in the Expert Ninja trophy description. Of course, instead of silently taking out the multiple hostiles in the area, simply use the G-MAL to down them and restart the checkpoint as required.

Chapter 22 - Dreamers of the Day

As you start this level, jump over the chasm to the stairs then enemies will spawn in set locations and one will come down the stairs. He carries a G-MAL so kill him and pick it up. Now kill the shotgun guy who comes down from the same way and the 3 guys in the distance, you should have plenty time before the heavy armour dude shows up so this equals 5 kills per restart of the checkpoint so is quite a good place to farm.