Really had to think about this, especially w/Polly's request for winners and bloopers thrown in!
Favorite tools:
Thimblelady S/S thimble
6 1/2 x 24 ruler fold away cutting table (folds to approx. 6" wide so on those rare occassions that I need to clean up the sewing room I can stash it behind the futon).Best personal winner so far is the folding snack tray that I can set up next to my machine for production work. It's large enough that I can put a small mat w/cutter on one side for trimming and fold up a towel to be able to press seams, etc. to continue sewing. Since I have the large table set up as well, I can use that for other stages of the project at the same time and keep moving along.
And thanks to this group, I haven't wandered into too many bloopers except the normal mis-cutting or mis-sewing of pieces!