Logic problems have been popular for many years; they appear in puzzle collections and there are several publications devoted exclusively to them. They often use a chatty, narrative style which makes them ideal for promotions that call for a lighter approach, yet their rigid rationalism also lends itself to a more serious form. Solving logic problems calls for a methodical, analytical mind, though they can of course be set to various levels of difficulty.
A logic problem contains up to four categories, each of relatively few elements, so they are best suited to the promotion of three or four products or services, particularly when you want to draw attention to particular aspects of those products or services. You could, for example, build a logic problem around the efficiency, the shape, the value and the colour of each of three or four household appliances. Notice that this would, again, require careful reading of your material by the solver.
Logic problems are a new departure in promotional puzzles, and if they suit your requirements would have the advantage of freshness and originality. They can be reduced to a brief answer for contest entries, along the lines of "Which appliance did Carol purchase, and in which colour?", if it does not suit your strategy to have the entire puzzle returned - for telephone entries, for example, or to add a brief contest entry box to your reply coupon.