(adsbygoogle = window.adsbygoogle || []).push({}); If you notice the pic next to each achievement, it seems to display the items used/to be used to get the achievement. Take the "Acquire Waffle Weapons" achievement for example. It shows the Wunderwaffe, Ray gun and the monkey bomb.

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Now here is the achievement pic for "Activate The Fly Trap" (notice how it says "The" ... meaning there's only one fly trap and it is not one of the normal electric barriers like those in Shi No Numa as stated in some interview)

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And I think this pic looks VERY similar to this device right below the eclipse

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Now as to what the fly trap actually does might need to wait until we actually use it but from the pics above my best guess would be that it generates a massive electric field fryin any zombie in its proximity. Maybe the characters actually stand underneath/inside it with the field protecting them.

What do you guys think?

I think your Theory is Correct.