A lot of the tourist shops sell hermit crabs as pets. Really, this isn't such a great idea.
We were sucked in, and bought two crabs (ah, the things you end up getting for the kids!) Most of the time, the crabs go into such a state of shock that they die shortly, whether it is from the wrong food, a trip in a hot car, not enough humidity, or a million other reasons.
If you're just dying to get a hermit crab, read up on them first, and get them from your local pet shop, not from a tourist shop while on vacation. They are finicky, and harder to care for than the tourist shops would have you believe. .
Unique Suggestions: If you want a souvenir, the tourist shops have many many other things... you will find something much more suitable, that won't die within 48 hours.
The tourist shops have a wide variety of beachwear, jewelry, toys, stickers, fridge magnets, and a million other things that can be taken home a lot easier.