What’s your vote for the most ridiculous, overpriced, and useless tweak?

I suppose you tried this outlet cover and found to be completely useless.....do you have any measurements to substantiate your vote? What receptacle did you pair this cover with? 

I vote there are no ridiculous, overpriced, and useless tweaks.

For me it was the horror of spiked loudspeaker stands. Some of these vandalising monstrosities even had spiked top plates!! Ouch!

After all the careful alignment and sitting of spikes through carpet (on crosshead screws no less) what was the improvement in sound? 

Bugger all improvement I'd say! Yet many voices, Linn amongst the loudest, were proclaiming that these items of ironmongery had to be assembled with enough pressure to almost burst blood vessels. Ditto for headshells.

Thankfully the alternative approach of a degree of loudspeaker isolation is now making a comeback.

Eventually we may even see a return back to the days when speakers used to come with small attached rubber feet.

My speakers, turntable, amp, preamp work best when spiked.  Everyone tunes to their preference.