This post is not about your small sack of tools that you carry around with you in case you get a flat tire, but instead about those necessary tools and tonics needed to keep your EDC gear in tip-top shape. Obviously what you carry dictates what will be in your toolkit. For me, a non-gun minimalist, I have a few go-to items in my EDC drawer.
First, I like having a lint free cloth. I got mine at the Container Store about ten years ago and it still works very well. Ones made for cleaning computer screens and LCD TVs work well. The microfibers will scratch nothing. I like using them to clean the lenses on my flashlights and the blades on my knives after a cleaning and sharpening.
A can of compressed air works well at cleaning those hard to reach spaces. If you can though, I highly recommend upgrading to an air compressor. I use one in my workshop and it works much better and is vastly more economic. It is not a requirement, and the cans work, but the compressor is nicer. Safety tip: be very careful when you use the compressor to blow out and dislodge things. For example, I used it to get a battery out of a battery tube. It will get the battery out all right, but with only one direction for the battery to go and nowhere for the built up air pressure to escape, the battery can become a bullet. I got a battery out of my Arc AAA-P and it made a large divot in the back of my workbench. It is two inch thick oak.
For cleaners, it becomes a touchier subject. There are some REALLY strong cleaners out there and they have done damage to my gear. Try to apply them on the edge of the surface or in some inconspicuous place first. Some denatured alcohol is also nice to have on hand for light cleaning. For tougher stains and grime I like the citrus based cleaners like Goo Gone. If you need something stronger than that, be careful. I have some Flitz Polish and Stainless Steel Polish (found at home centers because of the rise in popularity of stainless steel appliances). Rounding out the cleaners I have some Brasso for the heat sink on my Muyshondt Aeon. Be careful though all of these are caustic and need some ventilation to use.
Another go to item I like to have on hand is a series of micro screwdrivers. The Kobalt line from Lowes is cheap and well-designed. Also, if you break the Kobalt drivers there is a no-questions asked return policy (I have used it twice now). You can go all high end and get some Wiha drivers, but they are harder to take back if you destroy them. I recommend getting the drivers that have the bits in the handle--they are more flexible and are easier to store. The big series of drivers is really unnecessary and takes up a lot of space.
After a screwdriver set, I like to have a pair of tweezers for precision work. Nothing I have ever found beats the tip of the Tweezerman Tweezers. I know, I know: the beauty tool experts...whatever. You can get them in black, is that manly enough for you? Trust me, you will be thrilled when you can get that little tiny rock out of your favorite light's spring that would otherwise ruin your EDC torch. I have found them especially handy for manipulating shims and washers found in the pivot mechanisms of many knives. I don't know what the secret to their success is, but whatever it is, it makes all the difference in the world. I have never failed to grip something with a pair of Tweezerman Tweezers.
Next I like having a well organized and stocked supply of batteries. Here is a picture of my battery storage:
A few chargers help as well. All true flashaholics need a Nano charger for the RCR 123A and smaller batteries.
I also like to have on hand two or three kinds of lubricant. WD-40 is a requirement if you own a house or anything mechanical. I really like the dual nozzle cans. Plus it has that alluring clean workshop smell to it. I also like Rem Oil for more lubricant, less water repellent applications like the pivots on pocket knives. Finally, for those electronic components a contact cleaner/lubricant like Deoxit works very well.
I have a field sharpener, this one in particular:
It works well for touch ups. But for a full job I love my Spyderco Sharpmaker. There are more than enough reviews out there on this piece of equipment, but it works so well, it deserves a little more praise. I suppose you can go up to an Edge Pro, which does work very well, but for me it seems like diminished returns. There is also the full on grinder/polisher, but that requires more skill than I have. Though if I bought one it would a Tormek all the way. Tormek sharpeners are awesome tools for all sorts of uses, not just sharpening knives. They do, however, require a bit more skill than most sharpening systems.
Two last things that didn't really fit into any category: a magnetized parts tray and a Dremel. A magnetized parts tray works well when dealing with tiny parts. Plus they are cheap. Here is a good one. The Dremel is not so much for maintenance, but really an excellent tool for modding. Take a look at Griffin Hawk's Mad Max-esque Tenacious after it had a run in with his Dremel. They can cut, polish, grind, sand, and rasp like nothing else. Plus, Dremels are just too cool when you are messing around with stuff. It kind of makes you feel like a blacksmith and MacGuyver rolled into one.
All of these things can serve multiple purposes and I use many of them in my workshop. Having them all around just makes sure my gear is in tip top shape and ready to go.