Crysis

I done it in a very simple way:

At the beginning of "Assalut" after you go to the Commander at the Hilltop, there is a little boat driving around a little Isle down at the river.

The distance of the boat is between 230 and 270 meters, just keep firing at the boat, after 10-12 Shoots of the Precision Rifle the boat explodes and the achievement unlocks.

i got this one on the mission onslaught in my tank make sure your 200m away from the enemy and boom theres your achievement unlocked

Obviously the Precision Rifle is key here.

Best used against an enemy manning a gun emplacement (as they move less) and clearly in wide open area with a shot at the enemy.By pressing up on the D-pad you will open your binoculars, when in this mode, your HUD will display this distance to the enemy in yards, simply back up and wait until the binoculars reads 200m or more, hold B to go prone and eliminate your rifle sway, aim and fire.

This is best done with the sniper scope attachment on your rifle, however I unlocked it using the assault scope. Just keep your eyes out for that target of opportunity in the clear and let em have it.

Probably a bit late now, but i found an easier way while playing through the campaign.

In the level 'recovery' you'll be notified on a secondary mission to grab some intel from an HQ and to be careful of the patrolling snipers. Grab a precision rifle off one and proceed to the secondary objective, finish this and move on to the compound to recover the hostage you'll clear the peak of the hill.

Now the easy bit, get your binoculars out and and tag one of the gunner emplacements either side of the compound entrance (the one with all the land mines everywhere), if you're not 200m away go back further up the hill and try again. Easy to hit as they are stationary targets.

An easy way early into the game. Please let me know if there's anything that can be added.

It is possible to get this achievement early on in the very first mission ('Contact'), on Easy difficulty (possibly higher too, but I was having a tough time getting it on Delta).

After finding Aztec and dealing with the two guys on patrol shortly after, you'll head up on a ridge overlooking a building, with the objective of destroying a jammer. There is a boat patrolling the water, and if you check with the range finder on the binoculars, you'll see that it drifts between 130 and 200+ meters away- depending on where it is on its route. You can use your SCAR or an FY71 (if you've grabbed one) to pick off the boat's gunner from where you enter the area, up on the ridge.

I got this by putting my gun into single-shot mode (), and started shooting towards the nose of the boat, after it had turned and was moving away from me. After seeing a couple shots splash around the boat, the achievement popped from killing either the gunner or driver (it was too far away to tell).

Be warned- this may take a couple tries, as accuracy at this range is clearly not great on either of the guns you may have at this point. I'd assume the other solutions for this are easier, but you don't have to get as far in the game to give this one a shot.

I got mine on onslaught while I was in the tank. When you take control of the tank I simply stayed on the hill and fired at the tank from a distance. 3 shots and the tank exploded and I got the achievement.

I was doing this in my easy mop up.