The traditional gift is pearl or the modern gift is diamond. I've got a website with some gift ideas for anniversaries at www.anniprezzies.iofm.net (hope it's okay to put that. Why not? It helpfully answers the question! - AB Editor)
Can you give us some ideas about what you're hobbies are, how you like to spend time together etc? For instance if she loved Italy for example or you went there on your first holiday together on honeymoon, why not tell her that you'll take her out for a lasagne? But then book a trip to Italy for the weekend as a surprise and have a proper lasagne :) There are flights on ryanair at the moment that are dirt cheap.