Throwback Trophy in Uncharted 3: Drake's Deception
Kill 10 enemies with thrown-back grenades
How to unlock ThrowbackDuring your adventures you will meet a ton of enemies who think nothing of bombarding you with grenades. Thankfully in Uncharted 3 you can scoop them up and throw them right back if you get the timing right. Basically as they land close to you, you'll see a icon pop up if it's close enough to cause significant damage. To the left of this icon is a curved bar with a red sweeping marker that falls from top to bottom. In this bar is also a white block, and if you tap while the red marker is somewhere within this white block, you will pick up the grenade and toss it back in whichever way you are facing at the time. It's something of an art, as positioning the screen and timing the button press but when done correctly will result in a grenade being thrown back to it's sender and blowing them up instead.
There's every possibility that this will come naturally if you practice this method instead of diving for cover, the opportunities to throw back live grenades are in plentiful supply so don't be shy when you see the icon.
If you need a place to farm, Chapter 22 is ideal. It's right near the start and is also the best place to farm Throwback Master for killing 2 enemies at once. After clearing the stairs and the enemies in the distance, duck into the alcove at the top of the stairs and take cover against the archway. Many enemies will come to engage you but they will all stay behind the cover firing away like mad at you and throwing grenades. Headshot the heavy armour grunt so he doesn't spoil things and just wait for inbound grenades. Chuck them all back where they came from and restart things when they are dead. It will be a small matter of time and patience until you inevitably kill 10 and during the process very likely 2 in 1 for the other trophy. If you don't succeed killing 2 in 1 en-route to the 10, then just continue this process until you do.
Here's a video of this method courtesy of PowerPyx: