Free Puff Stitch Hat Pattern - B.hooked Crochet--I think if you eliminate the first rows of this pattern and use a crochet chain or a ponytail band, you could easily make this into a messy bun/ponytail hat!
Double Crossed Hat - A Free Crochet Pattern in 11 Sizes
This pretty striped hat is made up of crossed double crochet stitches. The Double Crossed Hat is an easy pattern and I have included photo support
CROCHET PATTERN - Top Knot Beanie, Crochet Knot Hat Pattern, Easy Crochet (Newborn to Adult sizes) Instant Download, pdf #025H
Ravelry: Top Knot Beanie pattern by Sarah Roberson
Hand Dyed Artisan Yarns & Unique Crochet Patterns by NorthernKnotsCanada