Looking for ideas.

Here's the thing.....My 3rd blogiversary is coming up next month and I want to do something fun for the occasion. Last year I did a give away but now I want to do something more than that. I want to do something interactive. Something that gets everyone more involved than just drawing a name from a hat. A real contest or something. So I need your help. Do you have any ideas for a fun contest? I have a few ideas but I want to see what you all think since you'll be the ones playing.