I gave each of my BM something different. They're different people with different personalities. They all loved that I got them all something different. Give them something that fits their personalities.
This isn't very fun or unique, but I got my BMs shoes and jewelry (necklace & earrings) to wear with their BM dresses... they were all really excited to not have to pick out or pay for accessories for the wedding, so it worked out. I've been in 2 weddings this year where the bride gave us jewelry for the wedding, and I loved it! One of them had the jewelry custom-made, and the other made them herself. That made it more special, IMO.
If you'd ask me, I'd definitely go for personalized gifts for my bridesmaids but I will also take into considerations the practicality purpose of the gifts. I am planning to make a purchase here at http://ericasweddingfavors.com/ they have lot's of very cute gifts for bride's maids and groom's men. You may want to check this out yourself :)