Just to be clear, PHOTOGRAPHERS don't collect cameras. COLLECTORS and HOARDERS collect cameras. PHOTOGRAPHERS buy cameras every once in a while as needed and learn to use each one proficiently and take awesome photos with what they have, over and over again, to the point, of wearing the camera out or outgrowing its features and abilities, and then, only then, do they buy another camera.
Below is a list of some classic cameras you can pick up if you want to actually use them in day-to-day use. They are more than just interesting looking, they are reliable and take quality photos while instilling discipline and knowledge. What you should really do is figure out what kind of photography you want to practice and research and choose cameras based off of that.
In no particular order:
Nikkormat FTn, FT2
Nikon FM, FM2n
Nikon F, F2
Pentax K1000
Pentax Spotmatic F
Pentax ME Super
Olympus OM-1
Olympus XA
Olympus 35 (any from the series)
Kodak Retina IIIc (or any other from the series)
Leica (any rangefinder)
Canon FTb
Canon Canonet (any from the series)
Yashica GSN Electro
Yashica 12, 24, A
Agfa Click
Agfa Clack
Voigtlander Perkeo
Mamiya 645
Mamiya rb67
Rolleiflex (anything)
Rolleicord (anything)
There are many many more "collectible" cameras that fetch insane prices just because they look cool or are rare, the list above are cameras that are prices well for what they are and can be used regularly when purchased at a reliable camera shop or after being serviced by a repair shop.
Buy from KEH.com, CollectibleCameras.com, CameraRepair.com, BHPhoto.com (used section), Adorama.com (used section), PennCamera.com (used section) or find someplace local to you.
DO NOT buy from Craigslist or eBay unless you are only interested in collecting and do not care about functional condition.
And one last word of advice, do not blow all your money on the camera, save a good portion for film, processing, printing and more lenses!
Check out the stuff I've written on my website about the topic:
http://www.johnnymartyr.com/martyrmusings.php
Good luck!
Metal & Manual! Film Forever!