High-voltage gloves are normally reserved for linesmen, ballsy sons-of-guns who service powerful electrical systems. They’re designed to prevent all but the highest voltages from causing any trouble, usually insulating up to 10kV. With high-power electronics creeping closer every day (hybrid vehicles, anyone?), mechanics will likely find themselves faced with a dangerous system at some point. Salisbury (manufactured by Honeywell) is the gold standard, manufacturing gloves in many sizes for five different voltage levels.
These are pricey. “Low-voltage” class 00 gloves rated for 500V start at around $70, and go upward to class 3 gloves with a 26,500V rating suitable for everything shy of high-tension wires. Those bad boys retail for around $120, but if you run into the nervous work of diagnosing high-voltage systems, suddenly the price becomes trivial. It’s worth mentioning that the gloves are fragile, usually requiring separate leather outers for protection, and they shouldn’t be stored folded or brought into contact with oil. Replacement is recommended every six months, since the compound gradually dries out. Quite a list of caveats, yet worth peace of mind. Lab supply stores online stock the full range of sizes and ratings.