It depends on the graduate's tastes and what they're planning on doing after high school, but in college way back in the "stone age" (late 80's, LOL) the gift I got the most use out of was a good dictionary. Mine was a HUGE Webster's that weighed a ton but was one of my most valuable resources for information, in fact I still use it 22 years after it was given to me as a graduation gift.
Have a music fan that plans on going to tech school to become a mechanic? Get them a gift certificate for a local hardware or music store, or a gift subscription to Popular Mechanics or Rolling Stone.
Budding beautician? Pick up another one for a beauty supply outlet, or create a gift basket of beauty tools (clips, curling iron, etc) they might need.
Computer fanatic? Gift card for Radio Shack or Best Buy, or a subscription to a computer tech magazine.
Believe it or not, there are some nice graduation (or any occasion) gifts out there that won't break the bank! I've made up gift bags full of dollar store tools, a pair of work gloves, safety goggles and the like for under $10. My "shade tree mechanic" uncle just loved it, because he knew that if he needed a screwdriver to pry something he wouldn't have to grab his good Craftsman set!