I have found, discovered and invented many over the decades, some of which are no longer useful because they are for things that no longer exist. I even had a monthly column in my bike club's newsletter. I now have many of them on my web site. Some are no longer useable because of - ahem - "advancements" in technology, but many still are.
http://www.wtv-zone.com/ChrisZCorner/tips.html Scroll down.
All of these have been used in the real world, some more than once. There are more, like removing cogsets without the use of a single tool, but these are for the most part obsolete because no one has the parts they were intended for. Although after reading some of the posts here I'm thinking maybe not completely out of use, so I might reinstate a few.