Really does depend what you want the camera for!
My "best bargain" was my *ist DL2 for £20 … it's proven to be an extremely capable infra-red camera, even unmodified
My K-5 is now my "knock about in the garden and on the beach" camera … robust, weather resistant and with a big battery which won't need changing during the day, under normal circumstances.
Sometimes I think the "baked-in" anti-moire might make the results slightly less than optimal, but mostly I don't even consider it
I've got nothing bad to say about the K200D, the use of AA batteries is in it's favour, but no particular feature stands out, in my mind.
Most of my other bodies "have their place in the scheme of things" … if you can find a KP, at a price you want to pay, grab it … it really is excellent!
The original *istD is surprisingly comprehensive, having twin e-dials, so intriguingly "advanced" to use, but it doesn't have any of the Custom Image or Digital Filter settings of the later models … and it needs CF cards, not SD.
The K-01 is a style statement. The picture quality is good, I love the looks of it but really struggle with the ergonomics … older eyesight probably doesn't help
I've steered clear of the bodies that need a D-Li50 battery simply because the batteries seem to be getting hard to find.
Purely my opinions, of course … inevitably YMMV
Enjoy!