From just a little bit of a couple colors of worsted wool, you can have a warm, snug beanie in practically no time at all. Great for stash-busting, gifts, and warm heads.

80-120 yards worsted weight wool (total)
Three color: 40-50 yards color A, 20-30 yards colors B and C
Two color: 60-90 yards color A, 30-40 yards color B

You can pretty much use as many colors as you want though.