A Kenmore 51 or my Singer Slant-O-Matic. Both are older than my parents(my mom is like 50?) I found them at the Salvation army for five dollars and fifteen dollars. Don't waste your money on new machines - they are garbage. For my 16th birthday I received a Brother. It didn't even last a year, and I remember the Elna 5200s we had in school always being sent out at least twice a year.
Look around garage sales for a good old machine... and like someone else mentioned, yes the Kenmore is loud as hell, I think because it is belt driven? My Singer is gear to gear and very quiet - it is my favorite but I don't have a table for it so I always go for the Kenmore (easier access?) and if you're looking for an old machine - don't waste your time on anything past 1965ish. You don't want plastic junk.