Everything. A tightly rolled magazine, a cup of a hot coffee, the ground you stand on.
Here is a link to a true story titled Don’t bring a knife to a coffee fight. Of course, a tool made for a specific task will usually work better than one you have to improvise. After sharing the coffee, there was one of these.
No shots fire, bad situation dealt with. Kudos to the author of the article.
Arms in the hands of citizens may be used at individual discretion… in private self-defense.