The simple chicken grit feeder, if you have chickens you should be giving them grit. This makes it easy as you can screw it to a post/wall and keep it off the ground a bit so it hopefully stays clean. 

I printed it without supports on an A1, the bridges were fine, but the curves were a little stringy so supports would help with that. It's just for chickens, so it didn't bother me. I also printed at .24 layer height as again, I don't think my chickens will care if they see layer lines. They are just happy to have grit.