Junk video that your kids have filled up your video camera memory card with. Usually you don't realize it until the crucial moment you need the space most.
Setup: You are filming the once in a lifetime event of your wife crossing the finish line of a marathon.
You: Here she comes, almost there honey, you can do it........ What the $%#@ Out of Memory.
You then view what's on the camera only to find 100 two minute kidvids of the cat sleeping on the couch mixed with jiggle camera shots of your kids making goofy faces in extreme closeup.