"What's in the box?"
"Pain." He felt increased tingling in his hand, pressed his lips tightly together. How could this be a test? he wondered. The tingling became an itch... The itch became the faintest burning... It mounted slowly: heat upon heat upon heat... . The burning! The burning! He thought he could feel skin curling black on that agonized hand, the flesh crisping and dropping away until only charred bones remained.
This excerpt from Dune exactly describes the feeling of getting a tattoo burned into skin using a laser cutter; however, this is just the feeling. When sight, smell, and sound are added, the process turns out to be quite an experience.
The sound by itself (meaning no body parts in the cutter), is probably the easiest thing to deal with. It is just the normal whine of gears, belts and cooling fans. When that sound is mixed in with the sensation of burning flesh, it turns the laser cutter from a simple machine shop tool to a futuristic torture device.
The sight is not too bad, just a light tracing its way back and fourth across the body. As long as you don't think about the fact that the small wisp of smoke trailing the light, is actually vaporized skin, everything will be fine.
The smell is bad. It does not travel far, but when you catch a whiff of the burnt flesh stench, it is quite nauseating. The thought that you have just inhaled some of those vaporized skin flakes, and they have settled on the bottom of your lungs, is the worst.
I am leaving a disclaimer out of this, because any person with access to a laser cutter who is dumb enough to try this, deserves what they get.