A must-have if you actually want to succeed at anything in No Haven. The RNG Rigger should pretty much always be used, the Rig Biomancy/Tweak Corruption are great for molding slaves and slavers to your liking, and the Reset Day means you can perform multiple tasks (including fucking) without having to worry about expiring missions. It's also great for recruiting when you get a Rare or Super Rare mission but don't have enough slavers to do it.
My personal favorite is Quality of Life though, because it lets you have more slavers and slaves than the core games allows. It can get buggy if overused, but that's due to how the core game is set up and Frank has been doing his best to work around it.