1. I used to work the night shift at CarMax. It got on my nerves that someone would constantly use the top of my cabinet (with an MDF top) to lay their dirty parts on, and then not bother cleaning it off afterwards. To be fair, though, once I put a note on it asking them to stop, they did.
2. I work with people who are pretty frivolous about their tools since the expensive stuff is provided for them. I will not loan my jump box out because instead of wrapping the clamps around the body, they're lazy and just clamp the electrodes to the body, scratching the piss out of the housing. To exacerbate things, they like to clamp them on the handle, making it less comfortable to carry.
3. My Craftsman laser-etched sockets. I got them exactly ten years ago and they've served me well, but the etching is fading on the most-used ones. I knew this day would come, but their easy visibility has spoiled me and I kind of dread moving away from them. It will be nice to have better-fitting sockets, though.