My suggestion is Time Control on Powder Toy. You know.. Speed up time, slow time, and even reverse time! It sounds amazing to me! Somebody please make it, either as a mod or a lua script. Thank you!

You can see the same suggestion in the Tpt Mod Forums here: https://powdertoy.co.uk/Discussions/Thread/View.html?Thread=18490

Ps- Could you possibly NOT make it a tool, but instead make it an element? Heres a short explanation:

It could be a dark gray (Or any dark color), and when turned on with Pscn, all particles around it will be slowed or stoped, and even can be reversed in time (Depending on maybe the tmp or temp of the time altering element). Also, the Time altering element lights up when on, and darkens again when turned off.

Whoever makes this element can name it if they want. But for now since it's my idea, I will name it "tael".

(Time Altering Element)