Doesn't have to be a material gift, could be an event, but all the same I'd like some suggestions.
If you want it to be a surprise, it's probably not a good idea to ask for suggestions here, where she will definitely see it.
Are you trying to buy relationship points with her by showing her you care? Is that why you made this topic for her to see?
I'm on to you sunshine, nothing gets past ol' Dancey!
Do something spontaneous and romantic, but don't do it on Valentine's Day.
I hate that people often need that day to be effing romantic...