In high school we had access to the Univac 90/70 at the local college. It supported interactive use via dial up terminals and batch jobs. There were exactly two slots in the batch queue. I wrote an assembler program which created a last-chance exit handler and then went to sleep. In the exit handler, it spawned two new copies of itself in the batch queue. Eventually the operator (who wore a NORML pin on his blue jean jacket) noticed a job was stuck in one of the active slots. So he killed it.
Later, he came out of the machine room and asked me to look at something. There were a whole bunch of stalled batch jobs and two jobs sleeping in the active slots. I calmed him down and showed him the equivalent of "kill -9" and promised never to do it again.