1. When I was converting a keg into a kettle, I needed to de-pressurize it first. I grabbed a screwdriver to press down the ball-lock without thinking about how much beer might be left inside. The resulting stale beer shower was not as much fun as it might sound. This time, I cleverly stood off to the side and finished de-pressurizing the keg, mopped up the stale beer from the floor and carried on.
A couple months later I hear my panic striken wife calling out that we have water damage on the basement ceiling. I rush downstairs, look up at the ceiling and say "No, that's just dried beer" and wander back upstairs, leaving her wondering why and how beer was on the ceiling.
2. The hopper on my grain mill is a 2 liter pop bottle with the bottom cut off. I bought it cheap off of a friend after it had been sitting in storage for 15 years (I supplied a new 'hopper' though). In my brilliance, I put a wide mouth funnel on top of the pop bottle, so that I could pour the grain into the hopper instead of scooping. Once the funnel started to fill up, it became top heavy and spilled over onto the floor. In my panic to try and grab the funnel, I lost my grip on the bucket of grain and it too spilt onto the floor.
I swept it all back into the bucket, crushed (one scoop ata a time into the hopper, without the funnel) it and used it anyhow. Well, except the stuff that fell too close to that nasty, grungy corner of the storeroom that the broom can't reach - that stuff got vacuumed up and throw away.