An impossible question, like asking if I had to stick with just one subject/theme ...
Tomorrow I'm taking out my Pentax K7 (digital colour) with a 43mm lens to shoot a music festival,
AND an MZ5n with the Orestor 100/2.8 and a load of Acros to shoot portraits. But next weekend I'll be loading up the Rolleiflex 2.8F AND the Triple Victo Whole Plate for a set of portraits. Best tools for the job? Definitely. One size to fit all? No such thing.
But if I were really stuck on the proverbial desert island and could only take one with me ... well, here it is.

It can do everything I need (at a pinch; I rarely do macro), in either 6x6 or 6x4.5 and is virtually indestructable. No silly rangefinder to kick out of whack, no linkage problems between trigger and shutter ('cos there ain't none), and it's already seen a lot of life since 1935 with its very excellent 2.9 Meyer triplet. Pre-owned, shot and cared for by both Mike Connealy and Les Gediman, it enabled me to grab the image that has kick-started a whole new arena of subject matter. And if it can do that even once then it's a camera worth working with,
n'est-ce pas?

It's also pretty. Maybe I'll pack it tomorrow.