I do the opposite. At least once a year I buy the techs that work on our printers pizza, sales reps from the few bigger places we buy free lunch somewhere, etc. The owner used to question it saying they should be the ones buying us stuff....
I can't count how many times they drop by to look at the printers free of charge, giving me advice over the phone, or just no questions asked submitted a warranty and have the parts mailed to the business so that I could install it myself... a $50 pizza saved us thousands. The sales reps will spend hours researching materials for me.... If I need to do a job at a cheaper price no questions asked they will drop it down...
All of the cheap swag that gets sent to me, calendars, cops, pens, keychains, none of them get used... Most just end up in the garbage.
If you really want to send your customers something, Tailor to their needs. If my supplier sent me a nice box cutter with your name on it I would probably use it everyday... Or a nice paper binder holder laser engrave if their name on it, something is actually useful in my day-to-day, those won't end up in the garbage.
You can never go wrong with pizza or gift cards, but of course those don't remind the customer of your business... Take them out for lunch, call them up one day tell him you're in the area and ask if they're free for lunch.. just shoot the s*** with them, don't try to sell them stuff and they will appreciate it.
Most of our sales reps are on very friendly terms with all of their clients, it keeps them loyal, shows them you appreciate their business, and keeps you in their mind when they need something. A lunch with the purchaser goes off a lot further than a calendar on the wall in the break room that the guy that does all the purchasing probably never even sees.
