no girl can resist handbags and shoes.
other than that take her shopping and spoil her rotten
That's a good idea, might take her shopping somewhere.
just got my wife a pauls boutique bag she loves it
What's paul's boutique?
Take her on a romantic weekend away 
I took her to london for a couple of days in january for a show/shopping trip.
If your really stuck, take a random household object, and wrap it up and sorted, she will be well impressed.
Works with all sorts:
Previous presents you have bought her, presents others have bought her, kitchen utensils.
Always works for me.
Think i might do this anyway

lol.
i had the same thing earlier in the year following the misus getting me a ps3 which is abit of a coincedence
we wnt to london n watched a show not the most manley thing but girls love that kind of thing mate.
We went to see joseph in january, when i took her for a shopping trip.
If in doubt tie a ribbon around it and say your the present. lol
I got my missus a private number plate for her 21st
If your fairly cretive you should be able to get one for around £250 all in
I managed to get the first letter of her first name, the day of the month she was born in and all 3 of her initials
I'll see what i can get off the dvla.