I liquidated most of my equipment many years ago, but my favorite was my old Rollieflex TLR.
Using it was a very aesthetic experience. It was so overtly mechanical, from the pop-up focussing hood to the crank film advance. The ground glass focussing screen image was a thing of beauty.
It was perfect for shooting candids. You could face 90 degrees away from your subject and just turn the lens to face them. Since you peer down into the top of the camera to focus, the subject rarely noticed that the camera was pointing at them. Also, the little shutter just sounded with a little whisper, which never attracted attention.
Working with the square format was interesting. Squares frame the subject more intimately than rectangles. the eye feels more constrained. I think that’s what made Diane Arbus’ photos doubly disturbing. She pins your attention into that square frame with characters to whom you’d normally give a wide berth.
Lastly, working with those huge negatives in the darkroom was a delight. Loads of rich detail there to be mined.
The downside, obviously, was a lack of flexibility in focal lengths. But that simplicity was oddly freeing, in a way. You just got used to seeing with that one perspective.