I first ran into a can of this wonderful stuff when I started my first job, and have found it invaluable since, to the point where I have a can at work, home, and even leave one at my parents’ house.
What this is, is a can of non-flammable, liquid, electronic cleaner that can be pin-point sprayed onto various powered-down electronic contacts which are often unreachable or time-consuming to repair/replace.
Smartphone power button not responding? DSLR knob not switching modes? Static in the line jack? EQ slider no longer smooth? Try some of this spray, and if it’s an electronic contact issue, it might just magically fix it.
Even after you’ve given them ample warning, the look of horror on the faces of your friends and family as you spray a stream of liquid onto their non-waterproof electronics is priceless. Even better is the look of delight when they realize there is no evidence of the liquid, and you’ve fixed their gadget.
Because it evaporates nearly instantaneously, you won’t end up with liquid damage to components or surroundings, is plastic-friendly in that it doesn’t discolor or crack it, and is safe to use liberally.
My personal favorite is the CRC Contact Cleaner 2000, since that’s what I first used, and I also chuckle a little when I use any product with the “futuristic” number “2000″ in it.
There are many fine products from competitors such as Permatex, B’Laster, and WD-40, as well, with varying claims of higher cleansing performance. Perhaps in really tough environments, this may be important, but for my typical home/office use, the CRC Contact Cleaner 2000 has worked just fine. Regardless of what cleaner you purchase, make sure you’re purchasing a version that is explicitly listed as non-flammable and compliant with all 50 states on low VOC (volatile organic compounds).