Depends on what you want...a 30 gallon will give you room for a couple of fish, but not too many - so you're going to want to pick personality-filled fishes. With a limited bioload you have to make each inch of fish count, so start browsing liveaquaria (Beginner Fish: Tropical Fish for Beginners in Saltwater Aquariums
) and see what appeals. Most of the fish in that section are hardy and generally out and about more often then in hiding.
Personally, for a tank that size, I'd start off with an ocellaris clown. Easy to keep, full of personality, can take a bit in terms of water quality variations...and it's a fish that will constantly be out and about and attracting attention to your tank. Take their gallon recommendations seriously - some of those fish can get quite large and would rapidly overtake your tank. Depending on your substrate a sleeper goby could be fun too - they're constantly sifting sand and out and about.