The most fun cameras I've used are instant film cameras, of whatever type. I think if I had an SX-70 it would be that, for its close focus capability compared to my Polaroid 600 One Step (and for its better lens). The Polaroid 250 I borrowed was pretty cool too. Really liked FP-3000B. Dammit Fuji! But the Impossible new bw 600 film is not too bad.
The other cameras I think are the most fun are:
- Barnacks, because they feel great in the hand, the lenses are great and they get friendly interest whenever people notice them (which is not often, and that is part of the fun).
- MF folders. So much bang for the buck - I love the Perkeo II for its petite size and the Bessa II for its superb large negs.
- OM1/OM4 for their size, egonomics and wonderful viewfinders. And lenses.
- XA. Shirt pocket, aperture priority, so easy.
- 6D with EF 40mm f2.8 STM pancake. Amazingly compact and capable full frame package, great in low light.
Least fun
- Yashica Electro 35 GSN. Large, hard to focus, but a great lens. Never bonded.
- Topcon RE Super. Large solid brick, well built but not pretty.
- any electronics-laden film camera
- any APS-C DSLR with small viewfinder