PSA: A playing card is the best shim I have ever used and I am not kidding

So last month I am hanging uppers in a 1920s house over in Dayton and the wall is basically a roller coaster. Nothing square, nothing level, the studs are all over the place. I burned through my whole bag of cedar shims in like 20 minutes because half of them split when I tapped them in behind the cabinet. I got mad and started digging through my truck for anything. Found a deck of cards my kid left in there from a road trip. Dealers, Bicycle ones. I folded one in half and pushed it under the low corner. That thing slid in smooth, no splitting, and it held perfect. One card is about .01 of an inch so I could just stack them until the bubble sat dead center. Needed three on one corner. Took me seconds. Now I keep two decks in the truck. Red for the left side, blue for the right, because I am that guy. The homeowner walked by and asked why I was playing solitaire on her floor. So what is the weirdest thing you have grabbed out of desperation that turned into a real tool?