Here is a great reversible scarf design, with an added twist (or three!) Firstly, it's knitted sideways, so although you have a lot of sts on the needle, you don't have to knit so many rows. Secondly, the fringe is KNITTED IN, so once you cast off, and sew in the ends, it's ready to wear. And thirdly, the fringe is made up of litle twisty tassels that are so easy to work. I loved making it, and it was completed in a weekend.
The yarn in the photo is Rowan Tapestry DK, which is a soft wool/soybean mix in random shades. The stripes in the scarf are just the natural colour changes in the yarn. Unfortunately this yarn is now discontinued, but any random or hand-dyed DK yarn in wool, alpaca or a blend would work.
You could also try different DKs, or try thicker or thinner yarns (changing needle size as appropriate) to make a smaller or bigger scarf.