11 Answers

Please don't make me choose just one...I can't imagine losing any.....

sight

sense of sight hands down...what can be more precious....besides love..!!

SIGHT. I could not imagine what it would be like without being able to see.

All of them are vital but to answer the question i would have to say sight

Sight because although I won't enjoy the bouquet of my favourite beverage any longer, I will still be able to locate the wine bottle and not spill it all over my shirt.

All of them are vital but to answer the question i would have to say sight

How about Touch... going through life not being able to feel anything around you. After all.. we close our eyes at night when we sleep. When sleeping, we don't really worry about smell. We turn the lights down low, shut noise levels down, and then we try to make ourselves as comfortable as we can with a warm blanket or soft pillow in order to FEEL comfortable as to fall asleep.  

speak

TASTE is probably the least important, although, without being able to SMELL, you might eat something that is rancid!  TOUCH alerts us to pain as well as pleasure, and the ability to feel is on the whole outside of our body (lots of skin).  HEARING, like itsmee said, would make the world an isolated kind of place, but my mom has been deaf in one ear for about 80 years and hard of hearing in the other....she still gets around pretty well for 92 years old. 
SIGHT is the one I would not want to lose.  I can still drive, go for a walk, see a beautiful sunset, my children and grandchildren, read and bowl, play golf, cards, watch TV (with captions), see all of your questions and answers, do my craft stuff, and so much more.  My mom has macular degeneration, which has resulted in my mom not being able to drive, and she has quit reading.  She uses a magnifying glass to read the newspaper.   My aunt had it, too, and it was devastating for her, as she did alot of crafts, and her mental state deteriorated as her vision became more compromised.

I was JUST thinking about that as I was going about my business. I couldn't bear to be without hearing. It would be so lonely. There would be no music. No voice. No sound of wind and rain on the roof.  That's it.