The liver, and here is why:
The heart requires cellular respiration to continue beating, as do the muscle cells for flexing.
The kidney is a close call, but it actively pumps fluids to filter blood, thus requiring cellular respiration as well.
Obviously the liver uses cellular respiration as well, however it is not as active as the other three organs. It produces large amounts of enzymes, and has a large chemical (rather than mechanical) impact on the human body.
A week or 2 at the most
Musculoskeletal
liver
the longest is 2hours
a fish has gone 44 without food
my mom
about a month or a week
Eight to Ten days.
Okay! You made that name up...right???
The flower that could survive the longest without water or sunlight would be a cactus. Now, you agreed to exotic gifts! Cacti have interesting looking shapes. You could get him a weird looking cactus. That would be funny, exotic and it would survive!
The Camel can survive longer than the Cheetah without food or water.
The answer is unknown but the longest anyone has ever stayed up is 11 days!!