Gunk it up with your skunk fingers

The act of ruining or soiling something that it is preferred would be kept in nice condition. Traditionally applies to brand new merchandise, cars, glossy or glass screened electronics, and other consumables.

"I opened the box for my brand new $300 universal remote to find that some asshole had already gunked it up with his skunk fingers and probably returned it."

"Oh shit, is that the new iPhone X*?? Can I see it???"

"No, you'll gunk it up with your skunk fingers!"

*Whatever the latest COOOLEST one is.