Protospiel is the premier game development convention hosted at several places in North America. The longest-running one is definitely Protospiel Michigan. The event has been showcasing "games from the future" in Michigan since about 2004 or so.
What you'll find at Protospiel are a few dozen game designers who have their latest creations ready to spring on the public. If you have designed a game, or dreamed of designing a game, this convention will give you the boost you need. Some of the best games at Protospiel go on to being published.
If you have any questions, please let me know. I'm not associated with the convention other than being a happy customer. I've made a pilgrimage to Ann Arbor almost every year since about 2006 for Protospiel.