If you're budget-restricted, your best bet is this Lydell NYC Pendant. It's a popular item, while not very costly. Another smart option is this Gurhan Pendant. While the price is not very high, be sure that this item will become a worthy addition to your wardrobe. You might also want to consider this Judith Ripka Pendant. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.
If you're willing to splurge, then you won't be disappointed if you check out this Konstantino Pendant. It's a costly but smart option. While you're at it, also have a look at this Roberto Coin Pendant. Yes, this item is expensive, but it does not mean it's not worth it. Why not also take a look at this Ippolita Pendant. You won't regret the money spent!