The most fearsome unicyclist ever...

[evil-nick]

http://www.noisebot.com/dinosaurs_on_bikes_t-shirt.htm

[john_childs]

Fearsome and fast. Looks like it's a raptor on the uni.

[Hazmat]

I would prefer this one on a T-Shirt actually. :D

http://www.suckertees.com/images/Built-for-speed1.jpg

[evil-nick]

But the snail isn't riding a uni... ;)