Hard candy is fairly cheap and can be put out in the lobby and conference room for visitors. It is a small cost but visitors will remember the visit when they put a piece of candy in their mouth (an extra they put in their pocket). You can select something else to give away to everyone (small products, company magnetic calendars, thick notepads, company pens, handy measurement handheld rulers, coffee mugs, etc.) but whatever it is, try to decide on something that is unique and will be remembered for being from your firm.