Difference Splitting Racks
These are the racks shown in one of my tutorials! They are both very simple and do very similar things conceptually but are useful in different ways.
The first one, Phase Dry Wet, takes in two signals, a "Dry" and a "Wet", puts them through an effect, and then cancels out the original version of the wet signal. This leads to the effect placed inside the rack acting as a sort of mixer for the 2 chains. For example, placing an EQ inside allows you to control the mix based on frequency!
The second one, Split Differences, instead puts one signal through the effect, and then separates it into two chains, one with the unchanged sound of the effect, and then the other with the effect phase canceled against the original signal. This allows you to easy split the differences an effect creates and process them separately. Very useful with things like transient shapers especially!
2 simple racks that use phase cancelation to seperate out the parts of a sound changed by an effect.