My ex bought me a signed Peyton Manning ball a few years ago but most women wouldn't appreciate that.
How much are you looking to spend? I love gift cards to department or clothing stores....and you can't go wrong with jewelry as long as you know her taste. Depends on how long you have been together. My last boyfriend and I totally overdid it the first year we were together...then every year after we downsized more...kind of like the relationship did.
Nothing wrong with gift cards/certificates (I love them) as long as you give at least one thing to "unwrap" also....a cd or book...and a nice card.