Side Arm Master Trophy in Uncharted 3: Drake's Deception

This trophy is way less hassle than it sounds and can be done in a number of ways. It stacks across Chapters and Playthroughs and you can die inbetween kills so the chain is maintained so long as you are armed and killing bad guys with your side arm. You can easily do this properly, as in just use your side arm, picking up new guns and ammo from fallen enemies to ensure you are always stocked up and don't have to break your chain with a melee/rifle kill. To do so, try to get headshots to conserve ammo and don't invite trouble by running into enemies as this will often initiate a melee sequence attack and break your count. Chapter 6-7 is a great place to do this as the enemies are plentiful, there's a ton of cover and most of the bad guys are armed with either a .45 Defender or a Micro so there will always a steady stream of ammo.

The alternative is to do the same as what's recommended in the 5 headshots in a row trophy description, being that you can kill a bunch of dudes with your side arm, hit and then Save Game, Then again and Load Game. This will respawn the enemies and also retain your kill count from when you saved it moments ago as well as retain your clip size, allowing you to farm the same enemies over and over. Try this in Chapter 8 - The Citadel when you get the TAU Sniper, it works like a charm considering you need 30 kills with that gun anyway.