If you're going to just be putting them on a shelf and showing them off, you're not doing yourself any good because you're not using them, and you're not doing us any good because you're shrinking the secondhand market with each one you collect. But if you're going to actually use them, any working one is fine.

I prefer Pentax cameras, especially the K1000; they're cheap, easy to find, the lenses are pretty good, and I can find broke ones on that auction site to use as parts cameras whenever the two that I use frequently need doctoring