It's really not about your age as much as his tastes, chica, but that being said, I'm fairly certain a dad would like any gift his daughter gets for him on his birthday. I don't have a daughter, but if I did, I'm fairly certain I'd love her gift even it was a pair of homemade socks when it comes right down to it. :)
Since we don't know your dad and what he likes that would be hard to say. I like rainnsurf's idea. It doesn't have to be hunting if you aren't into it, but a day where you go to the movies and a dinner, or go some place he used to take you as a child. My step daughter is 25 and when her and her daddy get together somehow the music from Aladdin starts to play. It is just something between them, but I must admit I like the smiles it brings to their faces.
Well what does your dad like? My dad likes to cook so every year I usually get him something that will be helpful to him when he's cooking. Try to find a hobby of his and work from there. Hope this helps!