Weapon Kill Achievements
Make sure to get the one gun achievement (only plasma cutter) on your first playthrough because it is the easiest to use and pretty much the most effect for a large part of the game. And a quick deterrant. Dont even buy another weapon on the first playthrough. If you shoot ANYTHING from any gun besides the plasma cutter, it will deactivate the achievement. I'd know. I just beat it today killing only with the plasma cutter and still didnt get it. As for the rest of the "30 kill with this weapon" achievements, carry around stasis packs and use stasis before trying to get the kill. Most guns besides the plasma cutter take a while to get the enemies down. The contact beam charges, the line cutter is a slow projectile, the flamethrower takes a bit of time, and the ripper is a bit confusing to control at first. As for the force gun and pulse rifle, stasis still helps because they aren't the most efficient killers when you're attempting dismemberment.
Hope this helps out in the long run. =)
Added by: CaoRen Dec 2nd 2008, ID#3581