I see this question sometimes on my facebook timeline and majority of the people choose "Heart":

Which part of the body organ never rest?
A) Eye
B) Nose
C) Heart
D) Brain
E) Ear

Here's my thesis:
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You hear of heart faliure? people holding their breath? people blind, and people deaf, but once your brain rests for one second you might/would be unconcious or die.. the brain is what tells all the organs in your body what to do. that includes, sleeping, heartbeat, breathing seeing, walking, talking, eating, dreaming and everything. most people think when you sleep your brain rests... lol if your brain rests, then what tells you to wake up? your heart? if your brain rests, why do you dream? well this question doesn't have one answer, so the nose and heart also does not rest, but you have to know that the last thing to rest in a human body is the brain (you stop breathing, your heart stops pumping blood to the brain and the brain takes about 10mins to completely die after you are in coma = death.)

source: http://gdevit.com/forum2_theme_111901284.xhtml?tema=8

none of the above

in this year...research have shown that the brain takes a tiny rest equivalent to a fraction of a second when you blink