When you are inexperienced it is not that hard to break test equipment.
The DMM:
Vaporized a probe set measuring mains voltage in 10 amp AC current mode.
Results:
Buy a replacement probe set. DMM no damage. Quite the surprise though.
The oscilloscope:
Probing an X10 appliance module and connecting the probe ground to the circuit ground then plugging in the X10 module.
Results:
Lots of sparks and magic smoke from the oscilloscope. This was expensive enough. I would not like to do this on equipment that costs US$6000.
The power supply:
Use constant current mode to charge a 2 amp hour NiMH 7.2 volt pack then try to CC mode to try to discharge the pack.
Results:
Internal fuse and reverse voltage diode blown. No sparks or magic smoke.
See, this is my point:
DMM: Any half-decent DMM will scream at you if you switch the multimeter to Volts mode while the probes are plugged into the current jacks. Also, it's extremely bizzare that the leads blew and not the fuse. Sounds like the fuse didn't do its job. Conclusion: you had crap gear.
Oscilloscope: I don't quite understand what X10 means, but I gather that you, in effect, connected oscilloscope ground to mains live or mains neutral? That should have tripped the GFCI instantly. Did this lab really not have GFCIs? Yikes! Was this a proper university electronics lab, or some random person's basement?
Power supply: Fair enough, that's just an awful thing to do to a power
supply. But here I take your point, I asked for an example of something non-contrived and horrible that students could do to hurt good quality lab equipment, and this is the one example you've provided that answers my question.