I think about this from time to time. A major element of my enjoyment of our hobby is actually using gear, especially 60's and 70's film cameras. By using I mean the actual, physical acts of holding the camera, adjusting the controls and releasing the shutter. The intellectual game of controlling the exposure with those adjustments is next most important, and the actual image is important only in the context of the two higher order enjoyments (I made this photo with
that camera). So an image from a K-1 is more enjoyable than a like image from a K-3, for instance.
Some of my cameras are a joy to hold and use and some . . . I keep mostly for their reputation. I think it is interesting that Phil and Steve have already mentioned two that I like, the KX and my absolute favorite film camera, the SV. KX feels right in my hand, like any Pentax S body camera, but also has the match needle metering, aperture window, perfect control placement and symphonic mechanical release sounds. SV has its own sweet, subtle sound, smooth advance and just perfect balance with a ST55.
The K, while a nice collectible, just doesn't have the same tactile responses, but it's fun to use because it's so old.
I just have never bonded with K2's. I like the Seikosha shutter but I hate the ASA ring. I don't like the MX - too small for my hands, and a SuperProgram has nearly the equal viewfinder (and I use it when I just want to rip some shots in semi-auto modes). MZ-S is in my collection for a similar reason, but with FA lenses - and when used with the FA Limiteds it rises to active enjoyment level, but only with those specific lenses.
My XA is just a really fun camera - I smile just deciding to take it for a walk, but Q7 is just a tool. I use it, but it isn't special. My Nikons (F2a, FE2) have that distinct heavy feel of over engineering, but the viewfinders (especially the DP-1) are a chore. I keep them because I think I should have a Nikon. (I sometimes carry the FE2 in my bag just to pull out when I get razz from somebody showing off a D810).
And then there are the LX and the K-1. The LX is a joy partly because I finally have one and using it satisfies a long-held fantasy.
And somehow the K-1 is nearly perfect. I need to sit down and write out why it is so, but that camera was built for me. I am strangely content now. I can sell things without regret - K-1 fulfills my equipment needs
and wants. The rest of my collection I keep for specific reasons and specific hobby uses, but most of the time now I put the other cameras back in the drawer and just take the K-1.