If you deal with a predominately male market, a pocketknife makes a nice giveaway.
This one is more than a knife -- it's more like a mini tool kit. And the more useful a gift is the more likely recipients are to keep it, use it and remember you.
Although we usually think of a man carrying this in his pocket, it could end up in a toolbox, or glove compartment. And don't entirely exclude women from wanting one. I know more than a few women that have one because they're compact and handy.
You may feel you need to avoid this as a tradeshow giveaway if many of the attendees board a plane to go home, since these may get confiscated at the airport. But just a sticker reminding them to pack the knife in their checked luggage can solve that problem.
I had one client bring imprinted pocketknives on an overseas business trip. The knives were a big hit. Prospects there saw the gift as novel yet practical.