This item is awarded in Self-Made quality to community contributors whose Unusual effects are accepted into the game through the Steam Workshop. Every Unusual Cap has the Community Sparkle attached to it, along with the Unusual effect that was created by the author.

If an Unusual Cap has an Unusual taunt effect, every taunt (with the exception of default and Unusual taunts) has that effect applied to them.

There are 893 known instances of this item (and counting up).


Source