Being hit by a proton particle beam inside a particle accelerator.

Fermilab has all kinds of particle beams from protons (very very dangerous) to electrons (pretty dangerous) to photons (dangerous) to neutrinos (not dangerous at all.) I worked at a lab with a photon beam, and we had two-person interlocks and booby traps and emergency off buttons and klaxons and all kinds of stuff to protect us from being exposed to the beam.

On the other hand, the neutrino beam lab had a sign that read “Please do not stand in the beam”.