I collect many tools, including some mystery tools, some of which have interesting shapes. Here's one of my favorites. I actually know what it is, but it took a long time and a serendipitous look at an old barn to figure it out.
As long as I'm here I might as well add a couple more favorites. There's one of the most unusual wrenches you'll find - made of what looks like cast bronze, it is, I think, a wrench for undoing some large hose coupling or perhaps a shaft gland. Who knows, but I like the form.
And then there's this constant velocity universal joint. Another one I was able to identify, a design surprisingly old.