For this USB I got a lot of inspiration from some of the Lewis Chess pieces [link]
Some of the defending soldiers have gone berserk, with crazy stares and shield biting. I had in mind to do a Viking themed USB and the berserkers fitted the shape quite nicely.
To prevent the cap from falling off there's magnets in the cap and in the main part, as demonstrated in the lower right pic. A nice effect is that when you take the cap off the upper teeth suddenly becomes the lower teeth.
...and you can make him talk. *hehe*