My favorite is my near mint 6VH Model 715 Dan Wesson I got so cheap, $269 plus shipping, with the original box, a holster, a gun rug, custom sights, 3 grips, and some parts, that I had to wonder what was I missing and why wasn't anyone but me and some other guy bidding on it? Why did he let it go so cheap? I was so relieved when the gunshop called to tell me it was in and it "looked really good". There was one on GB recently that went for about $650, and it wasn't as nice as mine is.
The S&W 28 I had was a close second. It had the target hammer and trigger, with an action job. It had a lot of bluing worn off, but was in great shape otherwise. I missed getting it back 20 years after I missed it by a dollar on GB! It looked exactly the same as the day I sold it. I always wondered what it had done during all those years.
In third would be the Dan Wesson "Frankengun" that I got when I went to a gun store that was going out of business and bought a very heavy box of "parts" for $50. There were enough parts to build an entire gun, which I did while eating lunch in the car afterwards. I made a ton of money on that deal, I kept two of 6 barrels in the box and sold the rest. There was a ton of stuff in there, a couple of cylinders, dozens of springs and several hands, etc. I sold most of it and still have some of the parts left. Never needed anything but a hand spring and a grip screw in any of DWs since then.