Dead Space 3

Best boosting spot is at the very beginning of Chapter 6, load it up, hit the elevator on the right and this will cause two regenerating hunters to instantly spawn. Use your weapon of choice (I used a maxed out line gun) and go to town, cut off the hunters legs, then their arms and sometimes you can get lucky and get the head for 5 dismembered limbs in one down. Go back and forth between the two hunters and get 8-10 dismembers every 20 seconds or so, there's also a stasis recharge on the wall by the elevator. Make sure to save and quit if you need to back out for any reason, I got my last 200 dismembers in about 10 minutes or so.

Note: Try and go into the level with 200 rounds or so, I exhausted all of my ammo right towards the end of my 200 dismembers, but the spot is right at the very beginning of the level so you can easily quit out and go grab ammo in another level then save and quit and level select back to chapter 6.

The best way to get this one is to go for the legs. Why? Because if you go for the legs, the enemy will still be alive, and will crawl towards you, leaving you another limb to cut off. If you go straight for the arms, the odds are likely that the enemy will die, leaving you only 2 limbs cut off.
Yes, 1 limb may seem very minuscule, but when you add it all together, you will need to kill around 175 less enemies to get this achievement. So it is saving you some time. Now get out there and do some dismembering.

This is mostly just to add onto A Silent Circus's Solution, but figured it's better off a new solution so people can see it.
If you're anything like I am and just kill things rather than be sure to strategically blow off limbs to get an achievement. You might finish a playthrough with barely over half. For instance, my first playthrough i finished with slightly more than 500 limbs. and then finished 2 more play throughs with barely over 600(in different modes and difficulties of course)
If you are like that, and you've finished the game on Classic mode like i did, load up and get your devil's horns gun. Add circuits to increase the rate of fire if you want to make it quicker, THEN load up chapter 6. The devils horns have A LOT of bullets in the invisible magazine I've only ever been forced to reload this gun once. I farmed 450 limbs in about 15 minutes. slightly faster than A Silent Circus's 10 minute 200.
Being the Devil's horns have huge damage capability, you really won't need much stasis if any. the moment they stand up and start moving they fall right back down for you, and with that rate of fire boosted up from circuits, this gun will be even more of a shock to them than without.

Credit to A Silent Circus for his hunter farming idea.