My favourite scarf pattern is the Yarn Harlot's 4-stitch pattern. I have made many of these....not as boring as rib, and a more interesting look to it.
Cast on 26 stitches.
Every row is: k2, k1b, (knit in the back of stitch), P1....repeat across the row.
Repeat this one row for pattern, for as long as you like. I like most scarves quite short so they don't dangle beneath my jacket, and I dislike wrapping them around my neck (choking).