Here's something I think all of them would like and you could always modify it a bit for each friend! Seashell votive candleholders!
Here's what you do:
First off, if you're close to a beach, gather lots of seashells and bits of sea glass and sand. If you're unfortunate (like me) and you don't live by the beach, check out your local dollar store. The ones around here usually have shells and sand. If they don't, go to the craft store.
Next, you need to find some globe shaped vase things. They're small round glass containers. You also want to find some glass votive candle holders that fit like lids on the globe vases. Buy them at the same place so you can find ones that fit together well. Sometimes you can find them at the dollar store, but usually you have better luck at the craft store. Buy some votive candles. I look for the ones in my friends' favorite colors or scents.
Now for the fun part! Pour a little bit of sand into each globe. Add a few shells or bits of glass or whatever other little trinkets you come up with. You can choose to glue the candle holder/lid to the vase, but I never have. Sometimes I tie a pretty ribbon to the top of the globe/bottom of the candle holder. Add candle and you've got a cute little gift that's fairly cheap!