Mice
In January 2010, I made a series of blown glass mice. The finished product looks simple, but the process isn't: it involves heating a glass tube and pulling to make a 'pod,' then carefully cutting and inflating the pod; securely attaching ears and eyes to the head; and finally, heating and bending the tail so that it doesn't kink at an awkward angle.
I made many mice besides the eight shown here; some exploded, some imploded, some were simply ugly. But in making mistakes, I improved. They say the best way to improve something is to practice. Glass will teach you that for sure.