Well, I don't recommend anything too expensive and gifts are nice. Most of the girls I know would prefer something that you do together, whether it is a trip (can be one day or more), or a day of fun things to go do...trust me, it is much more memorable. Last Christmas my best girlfriends and my bf went in on this "day out" kind of present. It was really cute and thoughtful. First they bought me all these cheesy dollar-sotre presents that I opened one at a time that represented what I was going to do...
Cheesy Present Real Present
Barbie Clothes Gift card to mall for an outfit to be used for the dinner
Toy Golf Club Round of mini golf
Rubber Ducky Day Spa/Jacuzzi rental
postcard of Seattle Dinner at the Space Needle
Then they gave me a little card with a map drawn out of where we would be going for the day...like a cartoon map of Seattle with dotten lines and the locations.
Finally They gave me a small empty picture album that had all the gift certificates and disposable camera to take pictures of the day so I can always remember it.
OK...I understand you are a guy and that might be over the top for you, but I was just using it as something to get the thoughts flowing. Maybe your girl is more into getting gifts, maybe she wouldn't like something like that?