If you want to catch Mother Nature at her best (and if by best you mean bizarre or darned scary), then look no further than how parasites hijack the biology of their hosts.
Take, for instance, the pseudacteon:
Though related to the harmless fruit flies breeding in the world’s neglected fruit bowls, Pseudacteon flies have a far more sinister appetite. The female lays her egg in the body of a living ant, and the tiny maggot will eventually move into the ant’s head to devour its brain. This won’t kill the victim, but will cause the ant’s (technically dead) body to wander aimlessly for days on end, until the ant’s head simply drops off from its body. The maggot will use the severed head as a pupation chamber, transforming into a new fly and finding itself a mate.
Gruesome, eh? Here are 9 more zombie parasites over at TopTenz: Link