30 Kills: RPG - 7 Trophy in Uncharted 3: Drake's Deception

RPG has a large explosive damage radius and is perfect for taking down armoured enemies, though the ammo is paltry and pick-ups are few and far between. There are a couple of good spots to farm the kills as follows:

Chapter 11 - Abducted

The area where you swim around killing bad guys from in the water with all the derelict boats and barges is where you will find your first RPG. Once this area has been cleared of enemies, make your way to the far side of the area opposite the way you came in. A bad guy will try to kill you with a mounted turret but he can be dispatched with a well placed grenade. Under him, in a small area slightly flooded is an RPG. Pick it up and bring it with you to the boat beyond, climbing the ladders to the mast (the same one with the first Tau Sniper weapon on it) and kill the dudes in the distance with the RPG. Kill 3 of the 4 guys then restart checkpoint as required.

Chapter 20 - Caravan

This area is just about passable as a farming area but not nearly as productive as the first. After you dismount your horse with Sully and proceed to clear the next small area with the PAK-80 dude, move further into the open air complex ahead of you. This area has a couple of different RPG pick ups but visibility is dreadful and consequently you may end up wasting rounds in the sandstorm which engulfs the whole area. It's still quite doable (especially on lower difficulties that allow you to venture a little further in before taking a shot) but the wise player would farm this in Chapter 11 and save themselves the trouble.