promotional products

Hello guys, I need your help. Which is the best promotional item that I need to use for our convention? My boss asked me to buy promotional pens, gifts and other staffs that we could put our company logo on it. Well, look up on the internet it gives me a lot of result and now I am confused which is the best promotional product that we are going to distribute after our convention. Aside from pens, is there anything nice and affordable item?