We used a 5kV (DC) power supply for an A-Level physics experiment, and we quickly discovered that could give you a pretty unpleasant zap (peak current was ~3mA

We used a 5kV (DC) power supply for an A-Level physics experiment, and we quickly discovered that could give you a pretty unpleasant zap (peak current was ~3mA IIRC, so not particularly dangerous - one of our teachers initially insisted on us wearing latex gloves, until we demonstrated it arcing holes in them so it just gave you a false sense of safety). We also destroyed a fair number of multimeters that were allegedly rated for the voltage[1] - they started displayed obviously erroneous values. I also discovered that accidentally holding a charged plate (thinking the supply was turned off) for a while could let you pick up tin foil just by holding your hand above it, which was pretty neat. [1] IIRC we used a voltage divider to keep the maximum voltage around 500V, and the meters were rated for 1000VDC.