The best traps for this achievement are
--Rivet Traps. You get these early, but it takes up to three shots to kill a splicer. On the other hand, you can walk through set rivet traps and easily pick them up.
--Proximity mine. These are sweet, but a little rare. One of these is almost a certain kill. Keep a distance between mines, they can set off a chain reaction.
--Electric Speargun traps. These are tricky to use. Don't walk into your own traps. Make sure both both ends are on something solid.
You can also use plasmid traps, but I found those hard to use.
Set these up before your little sister gathers adam. You could just shoot enemies with trap ammo, that usually counts.
This counts across multiple playthroughs.