Published patent applications. You're concerned that an unknown patent application will jettison your game. Keep in mind, you can't be sued for patent infringement until after a patent has issued --- that is, until after it's been officially granted by the USPTO. If you're concerned about recently published patent applications, you can review them at the USPTO's online patent gazette. When you review them, remember a few things:
- just because a patent application is published 18 month after filing does not mean it will be issued,
- even if the application is issued as a patent, you won't be liable for infringements prior to issuance unless you have been placed on notice, and
- even if you were placed on notice, you would only be liable for infringements that occur after the notification. In other words, you should have sufficient time to consult an attorney and decide whether to halt manufacture and sale before a lawsuit could be filed.
In summary, if you do withdraw the game in a timely manner prior to issuance, you will likely avoid liability.
Searching for board games. If you're searching for existing board game patents (not patent applications), this article should help. And if, after reading it, you feel your board game is sufficiently novel and nonobvious, you may wish to consider filing your own utility patent application, design patent application, or provisional patent application.