Car keys
Do not worry if you do not own a car, this trick can work for people who have anything else in their pockets or around them that can drop on the floor and not break. The reason for this is to stop someone from talking way too much and breaking their concentration.
If someone has been talking for a long period of time and no one else can get a word in, try dropping something to stop their train of thought and get them to be quiet for a moment. This will give you enough time to maybe jump into the conversation and get a few words in.