90V DC through a 10Ω resistor
During summer of 2014 I went to Tennessee's Governors School for Science and Engineering at the University of Tennessee, Knoxville. I took the engineering course, where we learned about a variety of different engineering fields. Fun fact, we visited more than 20 different university labs over the course of the 5-week program.
For the last two weeks of the class we got to work on a group project in groups of 4ish. I suggested our group try to make a rail gun or a coil gun. To my surprise, the course instructors actually allowed us to pursue this idea! For both a coil gun or a rail gun you basically need a lot of DC voltage or current, and capacitors to store it. The instructors helped us find a lab power supply (2-32V DC) and many old laptop power supplies to use, along with salvaging some capacitors from an old CRT monitor and purchasing a few online.
After a lot of testing, we were generally unsuccessful in making either a coil gun or a rail gun. We managed to get the coil gun to shoot a small piece of metal a few inches, but that's all. So one day I suggested we put the combined voltage all through a single resistor and see what happened. With the permission of the instructors (surprisingly again) we did exactly that - and the resistor burst into flames almost immediately. This is my favorite picture/video from all of Governors School summer camp.
If you try this at home, be safe-ish!