Been forever since I made a thread, so here's a fun one!
I love gadgets, especially useful ones.
First up, I have this GearWrench 1/4" drive Roto Ratchet
These things are super handy in tight spaces, plus I like how you can use them like a screwdriver once the bolt/nut is loosened up. Some people complain they are fragile (they are 72 tooth), but I think that has more to do with the tool being misused to try and break loose really stuck bolts/nuts. I've had this for several years and never had a problem.
Now for breaking stuck nuts and bolts loose, you need a proper tool, like one of these:
I have a GearWrench 24" Breaker Bar too, but this one is cool because it telescopes 18-24 inches. Really nicely made too. It's manufactured by Cal-Van.
Not really for automotive applications, but this is an extremely handy tool for removing and installing carburetor seats on small engines. It's made by Tecumseh.
It's always nice to be able to test your own battery, and while these things get quite hot, they are pretty useful at checking battery health by putting a load on them. The one I have is made by OTC.
Say you want to replace said battery, well you have to be careful if you have a security system on your car. Even if you don't its nice not to loose radio presets and be required to drive the car for the PCM to relearn everything. I had a simple memory keeper that plugged into the cigarette lighter and was powered by a 9V battery, but this one is more robust and has an indicator to confirm that it not only has power from the jump pack, but also that its connected to the vehicle successfully.
This is a Schumacher (OBD-L) OBDII Memory Saver Detector
No auto tool collection is complete without a code scanner. Mine is a MATCO Tools Determinator MD 2007. It's pretty old, but it gets the job done and can stream live data. It has some OBDI connectors too,which is kinda cool, although not all the ones this pictured one has. It's got the nice case though.
Finally, the coolest tool I have is what you use when you want to do more than just load test a battery. What if you want to know its exact voltage and CCA rating? What if you want to test the starter and alternator? This handy tool can. It's a Midtronics MDX-650P Battery Conductance & Electrical System Analyzer.
I don't use it much, and as such it stays immaculate, but it's been super handy a few times. It can do Flooded/Lead Acid, AGM Flat Plate, AGM Spiral, Marine, Motorcycle, and Lawn/Garden batteries. It can test CA or CCA in or out of the vehicle. It's also got a printer built into it.
What are some of the interesting/nifty/specialty tools you guys have in your toy chests?