Designed for repair

[tlynch]

After recent fun and commiseration over the serpentine belt tensioner on a 1995 E300D, I began to wonder what life would be like if engineers included ease of repair among their design considerations.

So here is my question:
What parts get replaced so often that cars should be designed to provide easy access to them using only commonly owned hand tools?

And related followup:
What is your worst nightmare story of a job that should have been easy, but was thwarted by the slimmest of margins?

I lead with serpentine belt and associated tensioning parts on a 1995 E300D. 10 minute job turned into a multi-day endeavor by 2-3mm of extra bolt length.

A neighbor told of removing a starter from its position fairly quickly only to find that he had to disassemble the suspension on one side to get it out of the car. Year, make, and model unknown.

Next?

Regards,
Tom Lynch