If you're wanting a modern machine - Hands down, a Juki TL98Q
While it only does a straight stitch it has a 9" throat/harp space, knee control presser foot lever, power foot controller with power & thread cutter pedals (there is also a thread cutter button on the front neck of the machine below the stitch regulator), needle threader, needle up/down button and this machine sews absolutely beautifully and works like a horse.
It also has an extension table which can be easily put on or removed depending on your sewing needs and comes with a good assortment of accessories and presser feet.
If you're wanting a Vintage machine -
A Singer 301 - mine is fantastic - sews only a straight stitch but stitches beautifully and works like a charm.
A Singer 500 Rocketeer - this not only sews a straight stitch, it does Zig Zag and a myriad of decorative stitches using Cams.
Any Vintage Necchi (only the ones MADE IN ITALY though - stay away from the ones made in Japan - they're mostly plastic with plastic gears, are not reliable and are not built to last like the Italian all metal machines) They truly are work horses and sew beautifully. I love both my Necchi BU Nova and my Necchi Supernova Automatica.
Good luck in your search.
It took me a while to find my Rocketeer but she's in near mint condition and sews like a charm.