Macintosh Centris 660AV w/original monitor + speakers (which are in the monitor) and original peripherals, 16 or 32MB RAM, 25MHz, 200MB HDD, System 7,5,3. Date of manufacture March 1992. Older than I am. Last used ca. 2009, currently in my dad's office under heaps of random papers... -.-
Macintosh LC II w/original monitor and peripherals, fully working + loaded, System 7,5,3 (I believe) ~10MB HDD, so on - currently protected by At Ease 1,0 that I must remove! I currently can't "use" the computer (i.e access Finder) but it is totally functional. Date of manufacture November 1992.
These are relatively "rare" systems, not because they were limited-production or anything, but because the Centris 660AV was superseded relatively quickly and the LC II was specifically for use in educational institutions and thus was not often found in homes.
The Centris 660AV is comparable to the Quadro 660, and the LC II is all but identical to the Performa 450.
I also have my mother's black MacBook 1,1 which runs 10,6,8 perfectly with a 1GB RAM upgrade and original 80GB hard drive (I believe). Early/mid 2006. Keeping this one for old times' sake.
We've got a 2006 iMac, from the first series using Intel CPUs if I'm not mistaken. It was running 10,6,8 but the HDC appears shot and you get that folder with question mark no matter how much directory maintenance and error-checking you do. I upgraded the RAM and I guess I'll work on getting a new HDD too!
I gave my mother a 2010 13" C2D unibody MBP with 128GB SSD upgrade. Aesthetically it's not too great, as I got it from a teenage girl! Works, though.
My primary machine is a mid-2012 15,4" MBP (MacBookPro 9,1) with the 2,3GHz 4C/8T i7-3615QM and 8GB RAM plus the high-resolution matte display. I put a 64GB SSD in the primary bay for OS X and applications and replaced the SuperDrive with the 500GB Hitachi drive that shipped with the laptop, which I now use for data. It's great for photo editing and intensive processing, of which I do A LOT, and also programming, which I should do more often.
I also bought my father an iMac 12,1 (mid-2011) which I believe has a 2,7GHz i5-2400S; I upgraded him to 8GB RAM. In retrospect, I should have waited a teensy bit longer to buy this one, since it would likely have been cheaper following the release of the newest iMacs in October 2012...but he needed a computer that supported the version of iTunes necessary for his iPhone 5, not to mention something not 6 years old!
Short story - my dad's a Mac guy and a gadget freak, and I've got all the technical know-how. As a family, we subscribe to the "waste not, want not" philosophy and thus rarely throw away or recycle any kind of appliance until the cost of repairing it exceeds its value. XD
Our washing machine and dryer are Maytags from 1991, so it stands to reason that we keep old computers around as well simply because they still work perfectly fine!
Also my dad likes "that game where you kill the Nazis," meaning Wolfenstein, which runs on our System 7 machines.