If you haven't heard of Shapeways and you're at all into 3D computer design, check it out. It's a service for printing three-dimensional objects made of lego-like plastic. That probably sounds like sci-fi if you haven't heard for 3D printing before, but it's quite real. What's unique about this service is its relatively low cost compared to most 3D printing shops.
For authors that are also into 3D modeling, or who know (or can pay) someone with that skill, this is a pretty cool opportunity. Personally, I'm planning on making a plastic model of one of the monsters from my current novel -- if it is published, that will be a pretty cool thing to have for giveaways, and as a talking point at any signings, etc. Definitely better than pens or buttons or whatever (though those have their place).
Maybe I should be selfishly hoarding ideas like that for my own personal use, but someone else is bound to think of it anyway. And really, hoarding good ideas is for lonely jerks. Let's see some durable, painted, limited-edition figurines of characters from upcoming novels!