The FrankenBook Pro
I built my workhorse computer around 5 years ago, after the logic board on my 2010 MacBook pro died (a known issue caused by Apple's choice of environmentally friendly solder which Apple would not fix). Rather than buy a $750 replacement board for an already 5-year-old machine, I decided to build an entirely new computer and use the hard drive and (already upgraded) SSD to save costs. However. I always kept the shell of this old computer, just in case.
As luck would have it, my brother had a damaged 2009 Macbook Pro, lying around with a completely destroyed screen. As I was sorting through old parts to drop off to e-waste disposal, I thought it would be interesting to see if I could turn two broken computers into one working one.
The interior layout of the MacBook pros between generations remained largely the same. Fortunately, batteries, Hard Drives, and RAM sticks are all interchangeable, so I was able to pick the best parts of each computer to use. The screen is what had me worried. The screens have two sets of cabling. One was similar between the devices, but the other was different. After testing, I discovered that fortunately power and video signal travel through the same unchanged cable, but unfortunately, Wi-Fi, ambient light sensor, and webcam changed between generations. It looks as though Apple moved the Wi-Fi chipset from the display to the base, and then shrank the cabling that runs from the motherboard to the display assembly.
Upon reconnecting, the computer powered up and booted properly. Given this early success, I thought I might try some inexpensive upgrades to improve performance and make it a computer people would actually want to use.
A $8 Wifi USB nub to get it connected to the internet again, and a $40 250 GB SSD to host the OS and apps for high performance. I also replaced the internal CD drive with an old 1TB hard drive for storing files (this 2009 MacBook has storage that rivals modern MacBook Pros). Updated to a modern version of OSX, I've upcycled junk parts to a fully functional (albeit not terribly fast) laptop from scrap for under $50.