My favorite suggestion so far and I'm sure Mom and Dad would be so proud! lol.
I think the gift card idea is the best. Save it and maybe add some more of your own money to it and get something really grand, like a tattoo of Neil Pearts kit across your back Just kidding. Let us know what you end up getting and HAPPY BIRTHDAY!
It depends on what you want. Go for something you need, rather than something you just want. If you want a drum DVD, but really need new heads, go with heads. You'll get more out of them than you would a DVD.