The senses
Touch
You know how they say that pain is good? Well, they're right. Pain tells you that soemthings wrong. Could you imagine getting getting you're arm cut off or breaking you're ankle without the pain. It might sound good, but without the pain would probably wouldn't even notice that sopmething was wrong until of course you looked and either noticed a bleeding stump instead of your fingers and you suddenly being shorter because you're walking on the side of your ankle.
(Note: when your foot hurts, rub it a lot. It reduces the pain (going to pull out some big words now) by stimulating the spinal cord's large fibers and closing the pain 'gate' in gate-control theory)
Taste
If you lose a taste bud, don't worry! They reproduce themselves every week or so. When you get old you lose a lot of you're taste buds and a good part of your tasting abilities.
People without tounges can still taste. You could even lose the ability to taste in one side of your tounge and wouldn't even notice since the other side would simply pick up the slack. We can't taste or smell nutrients (like fat, vitamins, and proteins)(sugar is the only exception)
Smell
We all have our own unique smell and our brain will recognize a familiar friend or family member's own smell before we even see them.
Body Movement
Something called our vestibular system keeps us balanced. Okay, now i'm going to teach you how mess with your vestibular system. When you spin in a circle very fast for around 25 secs. and suddenly stop it is humanly impossible to stand on one foot (I dare you to try it), here's something else that's fun to do to mess with your vestibular system. Get a partner and have them spin in a circle for about 20 secs. and then stop. When they do watch their eyes. What do you see. Now switch so they can see too!!