Food for thought here. What about a fire extingusher? Heavy enough. Just a thought as to what is in my general reach area while I am sitting in the drivers seat.
I have one in my car mounted underish the front passenger seat. I think its important to have
I almost expect the guy’s name to be Jack Bauer. 
I was trapped in my Jeep Cherokee several years ago when I live in CA after being rear ended by a Toyota Land Cruser that had exited the freeway at high speed. I did have a CCW at the time but fortunately I was on land and didn’t need to use it. I was only trapped by my seat belt and was able to cut my way out. I was a news photographer at the time and my cameras were, however, trapped in the back seat. One of the responding LEO’s suggested carrying a Spyderco serrated blade to make it easier to cut the belt and the tow truck driver was able to break the glass to get my cameras out quite easily with one of these (which I now carry everywhere I go, it is spring loaded and doesn’t require any effort to use):
