Great thread!
I have all formats from press to TLR to Hasselblad, but I'll put in a word for the high end 6x6 or 6x7 folder. Zeiss, Minolta, Voigtlander, Konica, and many others can be found dirt cheap on eBay and at KEH and other reputable dealers. The portability factor is huge - they will literally slip into a coat pocket and leave room for a meter.
Don't go for scale focusing in MF, you really do need the rangefinder, but it's still a very cheap entry point to producing the classic look and feel of the format.
If you're unsure about jumping into the big SLR pond, the Kowa models are cheap and easily repaired, with fine optics. They do sound like a Glock when you shoot them, though.
In the TLR field, the Czech Flexarit is still cheap and largely undiscovered by the collector community. Easily repairable by most competent repair people, and definitely a conversation piece. Nice optics and a generally reliable shutter.
On the subject of shutter speed in a medium format rig, if a shutter is consistently off in the same direction, it's pretty easy to compensate. You can get a decent idea of accuracy using a phone app called (surprisingly....) "Shutter Speed" which uses the phone's microphone to hear the opening and closing sounds. A more accurate "photo plug" light sensor is also available. Timing the shutters of my vintage gear has been very reassuring. Most of my vintage stuff is off by no more than 1/3 or 2/3 stop, which really doesn't make a huge difference in the field.
Andy