I made some birch beer soda Saturday. I put it into a 5 gal corny while it was hot. I figured no chill is only going to help marry all the flavors anyway, but it was taking forever. I had the bright idea to just seal up the keg and throw it in the pool. I'm certain I'm not the first to do that but it sure worked great. Minimal effort, no wasted water on the immersion chiller (although I do try to tun the immersion chiller water to the washing machine).
Anyway, damn simple. I started thinking about fermenting in them. I do 2.5-3 gal batches so my cheap 5 gal cornies are perfect. Pressurized transfer to my serving 2.5 gallon cornies is icing on the cake.