I am always looking for ideas and here are several that we have found that were unique. Micro -- chapstick container colored like a battery, we looked three times and found it each time but did not realize it until I pulled it apart.
Small container -- PVC pipe in the ground with a screw top in a busy city park in Nashville, you unscrewed the top and there was the container in side. Regular Container -- rock in a rock wall that was hinged and hollow, hit it with my hand and just did not feel right. Large container was a fake outhouse where the cache was the inside, peoples cards all over the wall and that is where you sign on a list on the wall.