When building defenses for rooms, I always add one Neurostun, one Smoking Gun, and one or two Prisoner Prods (usually two). If there are 5 slots I add Mechanical Pal (if there's a major module) or Pepper Spray. Neurostun is by far the most important for this achievement.
During the late game, some of the better setups involve combining 2-3 Tesla or Tear Gas Modules with 2 Neurostun modules. In an average sized room on Too Easy the 3 and 2 combination is enough to kill just about every mob.
Edit: Spending Dust to purchase items from a merchant counts as losing Dust. Don't mess this up like I did!