No matter how many dozens of socks I've made, I am still amused by turning the heels. It turns a three dimensional piece of knitting into a two dimensional thing, then back into three dimensions.
For those of you who aren't sock knitters, the cuff of the sock is at the bottom of the photo, the heel flap (the part at the back of your heel) is at the top. You knit the cuff around until your sock leg is long enough, then knit the heel flap back and forth (the two dimension part) until IT is long enough.
Then the magic happens, where you turn the heel into the little part that goes around under your foot.
Then you pick up all the other half of the stitches and knit the foot.
*I didn't really finish that sock that fast, the last photo is the first of the pair.