Kind of a trick question! Favourite camera.. for what I ask. One of 
my favourite for sure has to be the Hasselblad 500CM.. one of the oldest and longest used and still use to this day. Yes it is a film camera. Yes it is fully manual.. no ISO setting, no battery, no metering system at all and no autofocus. .. manual focus.. manual exposure.. 
film.. but a wonderful camera to use. Now on flip side I also enjoy the Nikon F4 as well and don’t want to forget it. I also have the F2, but the F4 is my go to film camera for the most part – and yes I do use it a lot more than my Hasselblad camera. I also pair it will digital Nikon cameras and they actually can pretty much share the same lenses which is a bonus – thank you Nikon! My digital team are the D500, D4 and D750. They all work together and each does a specific job better than the others. 
Now these are not my oldest working camera, that has to go to one I received from my dad. Although since I have received it, I have never actually used it. I did use a couple of times when young and my dad was still using. Yes has an aperture setting and shutter speed selection (although either is very limited). But is not an SLR and in fact the view of the image is somewhat a guess at best.
Bottom line there are many good cameras built over the years, and I have owned Pentax, Canon, Nikon, Hasselblad, Minolta, Sony, Mamayia, Polaroid and Kodak. I sold my two Sony cameras in 2018 and the Canon bodies before that. Today I only have the Nikon and Hasselblad (and of course the Kodak). Why? Well various reasons and for me I choose and keep what works and works the best for me. That does not mean the others may not work for you, but that they do not work well for me. Use what you have and enjoy your photography!!