Originally Posted by klinger86
throw a spare set of clothes a couple extra pairs of socks some tissues/mcdonalds or wendys napkins papertowels.... a couple blankets and towels..... spare shoes..... snacks to eat incase you get stuck for more than a couple hours about a gallon of drinkable water and non-drinkable water/antifreeze... when you switch your serpentine belt keep the old one as a emergency spare. and everything else other members have said....
Throw a sleeping bag in there and you're ready to go camping.
Seriously, one of those cheap $5 tarps 6' x 8' or so folds up small & used as a groundcloth helps keep you clean if you have to crawl around underneath. Also to lay tools on so you don't lose 'em in the dirt or grass.
I carry a few of those glowsticks you bend/snap to light, in various colors... taped a couple red ones to my tailgate once to get home after my tailights mysteriously went out.
Everyone has about everything else covered. I do prefer a large 4-way lug wrench over the wimpy tire iron, and a BFH comes in handy sometimes.