On my way to Columbus, OH we passed a road sign in Kentucky for "Big Bone Lick State Park". I couldn't talk my friend into pulling over so that I could get a picture.
And an antiques shop: "We buy junk and sell antiques"
I once worked at a school for physically and mentally "challenged" kids. I always cringed at the unintentional humor (or cruelty) of the standard-issue traffic sign reading "Slow Children" right before our driveway.