Example of a Rube Goldberg Machine
A Rube Goldberg machine is a contraption that achieves a simple task, often moving a ball from one place to another, through very complicated means.
This is a contrived example of emergence. Typically, emergent behavior is not designed and arrives spontaneously, while this is not the case it still illustrates the idea -- many simple things coming together exhibiting complex behavior.
For more information on Rube Goldberg Machine's see Wikipedia's Page on the Subject
For a particularly cool example see this video of a Japanese Rube Goldberg Machine cooking ramen: