I think we've all done it in one way or another; I've done some serious ghetto stuff along the way... like instead of paying for ramsinks aftermarket for a Radeon 9500 pro, I made my own with a dremel, arctic silver epoxy and pre-1982 pennies.
Probably the worst thing I ever did was to a TRS-80 model III. Someone gave me some oddball two-thirds height 80 track DD drives, that were almost an exact fit in the model 3 case once I cut the part of the bezel between the two full-height drives out (where the logo/badge usually is), removed like a third of the copper framework internally and gave it four coats of black and two coats of lac. It looked good, but I still feel guilty about having done it on some level.
Next closest would probably have been some of the stuff I had done to my original coco back in the day, which had a slew of bat-handle toggle switches sticking out of it for things like inverse video, execution suspension, switching between RF and composite output, etc, etc... I had also made my own version of the multi-pack and cut the top off the case to have it just kind-of sitting there on top of it.
In a way though, I kind-of wish I had both rigs still instead of having pitched them in the early 90's just because they were unique examples of what we were really doing with the systems at the time.
I keep thinking on giving my current Coco 1 with it's cherry picked parts a similar treatment, then talk myself out of it. Maybe someday if I find one of the all-black plastic ones to sandblast and grain-finish as a starting point then I'll do it.