So do you put all of your passengers in the trunk? Because god knows I don't want to get hit with a 150 pound friend!
No. I belt all of my passengers to their seats with safety belts.
Which begs the question, if your passengers don't want to get hit with you, will you ride in the trunk for them? But then who would drive...?
I belt myself down too.
I understand completely what everyone is saying but I refuse to live my life in fear, I take reasonable precautions to live safe.
Putting objects that could become projectiles into the trunk is, IMHO, a reasonable precaution.
You may think yourself a safe driver, and maybe you are. But what about the other people on the road around you?
Getting into the habit of using your car's trunk just helps protect you from the rest of the idiots on the road around you.
Many of the things people have listed here as being kept in their car are to be prepared for an emergency. A car accident IS an emergency. And in an accident, what can save you is not necessarily what you have in the passenger compartment with you, but what you DON'T have in the passenger compartment with you.
Car accidents are emergencies and it makes sense to prepare for them. Bring a first aide kit. Bring some flares, etc. But also prepare by storing those items securely so that your perparations don't end up being part of the problem.
Car accidents are emergencies. But they are common emergencies. Several folks here carry multiple pistol mags hundres of rounds of ammo, a shot gun, etc. How many major shootouts happen on American roads? Not very many. But these guys are prepared. Great. According to the Federal Highway Administration, in 2001, almost 220,000 red light running crashes occurred in intersections in America. There were 180,000 serious injuries and almost 900 fatalities from just people running red lights. You are significantly more likely to get T-boned by someone running a red light and have that box of ammo hit you in the head as a result than to be involved in a shootout and need that ammo. So put that brick of ammo in the trunk. That's the reasonable precaution.
Reasonable is about balancing risk, balancing different risks, and balancing risk with convenience. I'm not saying you shouldn't carry an entrenching tool in your car. But when you balance the probability to quickly dig a trench vs. the probability of an accident that could entrench that tool into your head, you quickly decide to put that tool in the trunk. That's a reasonable precaution to live safe.
Want a knife or gun to protect yourself from a carjacking? Ok. But I'll bet there are something less than 220,000 car jackings in America per year. I'll bet that far fewer than 180,000 are seriously injured in carjackings per year. So, a person interested in reasonable precautions balances those statistics and decides that if he does insist on having that knife for gun, it's going to have to be stored securely. I can assure you that clipped to the sun visor is NOT stored securely. Mr. cpirtle's knife appears to be stored securely. That form-fitted kydex holster bolted to the car would probably keep the knife in place even in a violent crash. That's the sort of thing you really do have to do if you really do want to be prepared to survive emergencies... because a car accident is an emergency -- a common emergency -- and an unsecured knife flying around the passenger compartment is not helpful in that emergency and does not contribute to your chance of survival.
My simple rule, if you wouldn't want to get hit in the head with it, either bolt it down or put it in the trunk, isn't living in fear. It's just common sense to increase your chances of survival a very common type of emergency.