All of the paint roller guesses were close. This is a holy relic from the earliest days of the Church of the Flying Spaghetti Monster. This roller was used to paint His Noodly Appendage reaching out to mankind in Michelangelo's masterpiece The Creation of Adam.

It's an ice scoring tool, sort of like a glass cutter. You take it to a frozen lake, walk out onto the ice, jab it in and mark a big "X." Then you invite your wealthy uncle who has no surviving relatives, except for yourself, and help him pick the spot where he'll plant his chair.

It's a tool for separating Lego bricks, or smashing them if they refuse to yield.

It's an alien can opener with the can still attached.