Your most indispensable "tweak"?

The beauty of tweaks is you don't ever need to narrow them down. 

This used to be my FAVE tweak until one of my eyes fell out of grace (doesn't track that well following 9 surgeries).

https://www.youtube.com/watch?v=erkpm6QggrU

Aside from that a decent equipment rack (even though my electronic gear is isolated by a double pocket wall from the listening room) as well as after market shelves for the source gear (Neuance/Greater Ranges shelves for the CD/TT decks) is way, way, way up there.

Cleaning electrical contacts for tubes and cables is also a big plus, but it's it's simply common/logical maintenance instead of being in the tweak catagory.

DeKay

Nano Diamant Contact Oil 
Zapperators

Dedicated 20 amp circuit  with an audioquest nrg power outlet and furman power conditioner. 

@redwoodaudio 

There is a big thread on them here in the forum. 

Can you link to this thread please?  Search does nor find it.