HALL OF FAMER
/Well, it would have to be sunscreen, boring! Although, if I was stranded on an island, my casper-white skin might help planes & search teams find me most easily, like the way they show people burning fires or using mirrors to signal over-head search teams, all you'd have to do is put me out on the beach, or whereever.
Assuming that hunky men would come to rescue me I'd definitely have to bring something. Question....would a palette be considered cheating? You know, one with shadow, liner, lips etc.. If so, then I'd have to go with a lip product. Narrowing it down to just one is another story.
To know me is to love me, I think. True story, when I was little we always took day trips to Bear Mountain (lake,camping etc) After a little sun exposure my mom would always put t-shirts on us, old school sunscreen. I was all of 4-5 years old and had a fit when she wanted me to put my shirt on over my adorable bikini. I refused to put the shirt on because, "Then the Life-Savers won't look at me!!" (I always called the 'guards' 'savers') I think that story is very telling. I really need to bring a palette, my bikini, and NO COVER-UP T-SHIRTS, EVER!!!! (ala Faye Dunaway as Joan Crawford in Mommie Dearest..."No Wire Hangers EVER!!!) Hope this story made atleast one person 
/I'm with beaush and Diana...I cannot even go a full day without using some sort of lip balm. I love Smith's Rose Lip Balm, not only is it great for the lips, but is also a multipurpose slave too. I've used mine on burns, to sooth rashes, and around my nose if it's chaffed (usually during colds). It'd certainly come in handy on an island!
HALL OF FAMER
/What a fun topic, Beaush!
This is a toughie and just the thought of being without powder, oil-blotting sheets, a lip pencil, and concealer is beyond comprehension. But if I had to bring one item, it would be my Clinique Superbalm Moisturizing Gloss in Currant. I can make do with oily, greasy skin, undefined lips, and an uneven skin tone. But having dry, chapped lips is where I draw the line!
BEAUTY MAVEN
/assuming the island has attractive native males? 
I'd say my number-one item would be a sweet pink hi-shine lip color, because it polishes off your face. In my opinion, people look the most stunning once they've been under the sun for a while---with that natural, exotic flush, so I think that a little lip color would be all you need.
I'd have to have SOME kind of lip balm with me since I cannot stand to have dry or cracked lips.. but WOW living without concealer or mascara would be tough! 
