tool most used on my Benz? Gear Wrenches.
The best tool in my tool box? the long small craftsman screwdriver. the third one down in this pic
http://toolmonger.com/wp-content/uploads/2007/12/DM_Sear5screwdrivers.jpg
my friend works as a mechanic, and he has all snap-on in his box, except for that screw driver. thats gotta say something.
the most used tool of them all? a floor jack. I have a Harbor freight one because is so damn heavy that it works great. not the best jack I'm sure. but for the money I'm very glad i bought it.
and the best tool i ever bought? my Toyota Tercel
I beat the crap out of it. and i use it as a tool, not a car. my Mercedes is my car. but when work needs to be done, its the tercel i turn to, cheap on fuel, and I've done everything with it. with extra low range, I've used it to pull cars out of ditches. it can do anything.