"Let's Hear About Your "Fun Collections"

Many of us stamp collectors have "fun collections" that are imaginative and out-of-the-ordinary. It might be fun to hear about them and maybe see pix.
Two them have appeared in another unrelated thread on this forum, a thread that was not about "fun collections" per se. That thread is titled "And Another Thing- U.s. #1036." In it, John Becker describes and shows his "fun collection" of mute ovals and ZebraMan tells us about his 365-day calendar of SON's.
There must be others. Let's hear about them!

When breaking down US collections I see many common commemoratives. I was fascinated by the Pray for Peace cancels. They seem so out of place in today's society. I started a collection.