This has got to be one of the simplest little hardware hacks I've done, but perhaps also one of the most effective.
I've owned four generations of Mac notebooks, and several other Apple products besides, all featuring variants of the same basic power adaptor design: the squarish, rounded white brick with flip-out wings for wrapping the low-voltage line for storage. Many of these power adaptors have not stood up well to everyday use - though to be fair, I do mean I use them pretty solidly every day. One of the early adaptors for my iBook developed a short on the 120/240v side. The magsafe adaptor on my latest laptop, a Macbook Pro, had the low-voltage line pull out of the rubber strain relief sleeve attached to the brick, exposing the internal wiring.
I've seen the same issue with machines owned by a number of friends. In all of these cases, Apple replaced these quickly and with no fuss. I'm pretty careful to leave a little loop of slack before I start wrapping cords, and I never apply force directly to the cords (e.g., picking the adaptor up by the cord). And although it seems that the designs have improved and the the adaptors have become more reliable over the years, I didn't want to have to go through the time and effort of replacing the power adaptor again.
When I looked closely at the strain relief moldings, I could see that they were not actually attached to the cord. This is what allowed the cord to pull out in the last adaptor I had to replace. I decided to put a tiny drop of cyanoacrylate glue (Krazy glue, Super glue) and work it into the gap, on both the high voltage (thick) and low voltage (thin) cords. Two minutes later, and the cords were very solidly anchored to the strain relief moldings. I've had no sign of trouble since. Rubber to rubber contact is one of the best combination of materials for this type of glue, so I'm pretty sure I won't have to deal with this particular problem again!