Limiting myself to cameras I've owned, in no particular order other than starting with an RF since this is RFF:
Yashica Minister 700 - I now have a Lynx 5000 instead, but I preferred the Minister 700 and wish I'd never sold it.
Olympus OM-D EM-1 mk1 - I have the mk2 as well as a EM-5 mk1, The mk2 is certainly a better camera, but I just know my way around the mk1 so well I still use it as much or more.
Olympus OM-2SP or OM-40 - This is a toss up for me. I've used both on trips, and I love both. The 40 is smaller, lighter, more comfortable to hold, and has a better light meter in my mind. The 2SP feels more robust. Both set the shutter speed via a ring around the lens base, and I think that has got to be one of the best manual controls on any SLR.
Bronica ETR-Si - I use it as both a big honking SLR with the grip and prism finder, and I use it more like a TLR stripped down with just the WLF. I love it in both, and making darkroom prints from a 120 negative makes me wonder why I ever bother shooting 35mm.
Canon AE-1 - As a camera body, it's (slightly) inferior to the OMs listed above, but it has sentimental value (I'm using my Dad's camera), a great view finder, and the lenses on it are amazing. Bonus points to the AT-1 which is a cheaper less loved version that only differs in having a cheaper light meter and does without auto-aperture mode. Since I only use full manual mode and often shoot sunny sixteen, the AT-1 is every bit as good at the AE-1 and gets just as much use (strangely, they both get way more use than the T-90).
Honourable mention to the Exa 1a with WLF for being a very endearing camera with a tonne of character while being a right royal pain in the ass to use.
