My current favorite is the Pfaff 60 treadle straight stitch, its a lovely machine. So quiet and smooth running. Next year it might be the Singers 15-90,201,237 or 66-1. I also have Singers 221 and 301, all are lovely machines that sew great.
For sewing folded corners on quilt blocks I prefer a straight stitch machine with the original foot(I'm doing those now).
I've got several different brands of machines all of them have their quirks and different uses. I have a newer Viking with all the bells and whistles, I'd rather use one of the vintage machines. She sulks when I neglect her.
Sharon W.
sewing machine junkie