I could live without my ball winder as I could use a pvc pipe as a Nøstepinde. I could live without my carder, if need be, as I could hand card with dog brushes. I could live without my spinning wheels, if I had to, because I could make a spindle out of almost anything. We all have different physical limitations and strengths and some decisions would be based on that, of course.
The tool I must have, must keep above all others surprises even me, but it is my Babe's Electric Skein Winder. I just love this thing. It works just as well as you could ever want. And you can stomp down on the pedal and really make that sucker fly. Or not, if you want a soft and gentle winding. I know, you are thinking, 'PVC, who wants a big white thing in their fiber studio?', aren't you? Well, I do!
I love tools that work well. And clean up well. This may not be an issue for some, but have you ever wound off skeins of Angora? The haze can get everywhere. Wipes up with a wet paper towel. Or commercial mohair? I once wound 6 lbs of mohair that had been in 2 oz balls. Think about that for a minute - a mountain of fluff. It had all been in a musty basement and was stinky, but a severe bargain. How long would you have been winding it into skeins by hand? It took about 45 minutes by hand and would have been faster if I could have tied knots between balls any faster. Blazing speed.
You look at this simple tool and think that it will be too flimsy for use, but I beat mine to death and it works well. From spinning wheel, bobbins, yarn balls, or cones, it really flies. My biggest criticism is that it is just a hair larger, skein-wise, than my adjustable LeClerc winder that lives near my ball winder. That tool gets used less and less these days.
What is your must save tool?