The pattern is written for making a keyring / handbag decoration,
For the Head:
 DK wool (appr 95m for 50g)

2mm or 3mm hook

Any fluffy wool for the mane
For the Horn: 

Crochet cotton, no. 8

0.75mm or 1mm crochet hook

Craft pipe cleaner bent in half
Hollowfill
2 brown or black beads for the eyes
1 Keyring

However, varying the yarn and the hook sizes you can create anything from earrings to brooches and cuddly soft teddy Unicorns using the same pattern.
Earrings: 0.75mm hook, sewing thread
Brooch: 1.25mm hook, crochet cotton no.10
Soft Toy Unicorn: 10mm hook, and super chunky yarn from 2 skeins