My favorite has to be the 3v spark plug remover by Lisle, used to remove seized and broken plugs on the 5.4 triton. Saves 300 dollars per one cylinder and my life saver.
A church key. It gets used after every job!
B’Laster PB comes in a close second…
It doesnt always work right, but my favorite tool is still my brain, such as it is.
Sorry to be a pest but…Am I allowed a real big tool…like a tractor. I use it for every thing from towing, grading snow removal, moving furniture, gardening, taking grandchildren for hay rides etc. It’s not a real cave man tool, but I couldn’t live as well as I do, where I do and as safely. No “man” should be with out one…regardless of how small or big; they are all great.
Craftsman basic socket, ratchet & wrench set dad bought me when I was 16.
Still have all of them including dad, 81.
I’m now 54.
I have to agree with meaneyedcatz that the best tool is wisdom. My favorite tangible tool is my three-jaw puller. I got it just recently and have used it only once, to remove a stuck brake rotor. Despite of the fact that I’d never needed one before, it has many useful applications, and it looks cool, and I enjoy watching it work.
It’s decidedly not a caveman tool, but it’s a refined, and more effective, replacement for caveman functions yank, pry, and hit.
Do something special with him soon. I wish I could. I got my love of all things automotive from my dad.
Um, Ron, that’s your favorite tool, not Wall Street’s…
" No “man” should be with out one…regardless of how small or big; they are all great."
dagosa, are people going to question your manhood now like they do the H1 owners? Enjoy your tractor. 
My favourite tool is whatever the right one for the job at hand is. In all seriousness, the one I’m happiest to own is my torque wrench, but they all have their place.
And if people are allowed to say “knowledge”, I’m going to nominate my Utilikilt. It’s basically a cross between a toolbelt and a kilt, and keeps the tools I need close at hand.
Favorite tool is any type of magnet, which has cneme to my rescue many times. If the pencil extension magnet wants to stick to eng block, I stick it into a custom cut piece of pvc pipe .
McNutcase, The “Updraft” You Undoubtedly Get Wearing An Automotive Kilt Must Be Welcome Relief From The Summer’s Heat. Sounds Comfortable. I’m Just Not The Type To Make Any Mechanical Fashion Statements.
CSA
Sometimes there’s a fine line between toys and tools.
A curse we tractor owners have learned to live with…AKA, Tim the tool Man, agrrrr…wo wo wo.
Dagosa, That’s Definitely The Situation With My Non-Contact Infrared Thermometer, But It Does Both Quite Well.
When I use it the cat chases the laser pointer and just like when I use my Radar Gun, anybody standing near wants to have a go at it. They’re both fun.
I think what we’re seeing here is that it is fun or gives one much satisfaction owning favorite tools even simple inexpensive ones.
One of my favorites (now retired) was a crescent shaped Snap-On box end wrench that would reach right around back of the little intake manifold on “Old Beetles” and get the nut back there and make a difficult carb removal / replacement actually fun.
CSA
BFH
Oldwrench, That’s One Of The Earliest Stubborn Parts Tools Known To Mankind, Originally Made From Rocks. Mine Is Steel and Weighs In At 13 Pounds ! It’s Hard To Find A Tool More Satisfying At Those Frustrating Moments.
CSA
A BFH is particularly satisfying when used with - an impact wrench!
My all time favorite tool is a speedhandle. It’s what we used to use for speedy insallation and removal of screws, nuts and bolts before cordless drills were invented. Mine still gets regular use.
Not a tool for repairing a car, but for use on a car/truck…the ratcheting tie-down.
You can either buy rope, tie one of those knots you “kinda-sorta” remember from Boy Scouts, and spend the entire drive apprehensive…
…or you can pony up $7 and get the right tool for the job, and not worry.
My dad’s one of those guy who doesn’t like to spend money on…anything, so we hauled a lot of canoes, matresses, etc, the first way. Then I bought my first ratcheting tie-down, and appreciated having the right tool for the job!