Dyno-Might Master Trophy in Uncharted 3: Drake's Deception

There's one location in the game which is by far the most popular place to earn this trophy, in Chapter 16 - One Shot at This but I actually got mine later on and found it a little more reliable.

The first place is as I say, in Chapter 16. During the part where you climb up onto the hangar roof, watch through the open skylight for a patrolling guard and press when prompted on screen to jump down and perform a stealth kill, note that you need to kill him this way or he won't drop the grenade. After you pick it up, shoot the locks off the hangar door to let Elena in. After this, a jeep will pull in from the opposite side of the hangar. 4 bad guys will exit this vehicle at the same time and yet 3 more will run in from the left, your ideal grenade spot is directly to the rear of the jeep. More often than not you will blow up at least 4 guys and the trophy should pop soon after. Below is a video guide of this courtesy of Pesico:

The other way is in Chapter 19 - The Settlement. After the cutscene where you dodge an RPG and come under fire from a huge vehicle artillery on a supported platform you will automatically take cover. Once play resumes, keep a careful eye on the bad guys taking cover behind the supporting beams under the vehicle, they love to throw grenades down at you. As soon as you see one of them do the animation, pop up and squeeze a shot off at him and he will drop it. Though you won't actually see them all, there are 4 guys who like to hang out under that platform and more often than not, you will take out all 4 and sometimes, you will even blow the supports and bring the vehicle down as well and they all count towards Throw-back Master!