Finder's Fee
This item is awarded in Unusual quality to those who report major economy-breaking, remote code execution, or otherwise calamitous bugs, and provide detailed information and steps to reproduce. It is possible to receive more than one Finder's Fee. The recipient may also choose what Unusual effect they wish.
There are 16 known instances of this item (with various unusual effects).
Source
Source
Unusual Finder's Fee
Team Fortress 2 Limited Level 50 Hat
★ Unusual Effect: Green Black Hole
Halloween: Voices from Below (spell only active during event)
If you own this hat, that means you reported a major economy-breaking bug or a remote-code-execution bug and made the game better. And that means you're an admirable person. Like Gandhi (who also owned this hat).
( Not Tradable, Marketable, Usable in Crafting or Gift Wrappable )