My MacBook 5,1, the first aluminum unibody MacBook available. It's been very reliable machine since I've owned it and operates almost flawlessly. I've upgraded to 8GB of ram and an M4 SSD, running Mavericks. I feel pretty sentimental about it, not even overstating that. It's going to be upsetting to let it go, but I think it's time for a change in the near future. The build is no doubt the best I've ever owned on a laptop of any kind. It would have been really nice if Apple chose to keep the door on the bottom to replace batteries on demand with their notebook designs, or even the option to upgrade RAM and hard drive.
It still shocks me every day that this computer is still running so well considering how old it actually is. I can't say that I've ever owned a laptop that has lasted this long and given me so little trouble. ACER, Compaq/HP and dell all failed me in under two years before I switched to Apple.
It's mind boggling to think my MacBook is going on 8 years. The build is so solid that it still looks like new money. Great product!