TFI-IV ignition module failures.
Aluminum piston cracking on Taurus transmissions (early 90s?)
Plastic waterpump impeller failures on early Duratec 2.5L V6 engines in the Contour/Mystique
Engine wiring harnesses made with incorrect insulation (was PVC, should have been XLPE), causing the insulation to crack and fall off, 1995-1997 Contour/Mystique
Ford Crown Victoria Lighting Control Modules with poorly-soldered headlight relay, causing headlights to fail (they finally issued a recall for this).
3.5L V6 engines with waterpump designed to require massive labor (several hours) to replace AND which fails by dumping coolant into the engine oil, resulting in engine destruction
(EDIT: Forgot the steel ac accumulators they wrapped in a foam insulator to GUARANTEE that they would corrode and start leaking. Easy fix, rip that wrapper off...I once paid $200 to the local hee-haw Ford dealer to fix this problem and that was all deductibles on the extended warranty I had. $50 deductible, 4 trips. Took them 4 trips to figure out where it was leaking)
and my favorite
1987/1988 Ford Mustang with foglights, using the foglights would cause the thermal breaker in the headlight switch to open because they never increased the wire size to account for the additional current draw of the fog lights. (IT appears that the original design had the foglights powered off the main headlight circuit before it got to the multifunction switch (which selects high and low beams), then someone figured out that regulations don't allow foglights and high beams to be on at the same time, so their "quick fix" was to simply redesign it so that the low-beam circuit powered the foglights. At least that's the only reason I can figure for there being a larger wire gauge going into the headlight switch than coming out of it...engineer forget that the current in a series circuit is the same at any point?)
I'm trying to remember what the deal was with the cruise control switches that would catch fire. Did they run unfused 12v through them?
All manufacturers have blunders like this. We're covering like 4 decades here.