Staring down the barrel of a laser.
This isn't exactly the National Ignition Facility, but still there was a sense of danger in looking at the business end of a laser through a 10x microscope. Fortunately for my eyes the laser was unplugged.
After many years of service, my Sony external DVD writer is having trouble reading DVDs, even ones it wrote.
So I opened it up on the off chance that I might revive it by evicting a dust bunny or two. Nope, no dust bunnies here - it was surprisingly clean inside.
I gave it some gentle blasts from a compressed air can, and wiped the lens surface with a microfiber cloth.
It survived my ministrations, but I don't know yet if it reads any more reliably.