Garter stitch is knitting at its simplest.  You use the knit stitch for every row, meaning that you get bumps on both sides of your fabric.

The lovely texture this produces works especially well with superchunky yarns like Rowan Big Wool, Blue Sky Alpacas Bulky and Spud & Chloe Outer.  Why not try a garter stitch scarf with one of these yarns?  A couple of balls of Big Wool or three or four hanks of Bulky and Outer will make a nice length scarf 15-20 stitches wide.