My only rule with goodie bags is that the sponsor items should be things that people will need anyway and that need to be replaced often or you need multiple of.

Good examples are pens and spiral notebooks, one can never have too many. Really bad things I have gotten are rubber wristbands and a "phone holder" that was supposed to hold the phone in place while charging.

Also emphasis on the "replaced often" part. Most people will probably use a bottle opener or a keychain thing, but they only need one. What is the chance that they needed one right before the event and that they will keep using the one the event gave them? Or for example, water bottles seemed like a cool idea when I first got one from an event, but now I have 5 water bottles with sponsor logos and I still only use the one that came with my carbonated water maker.