Interference is a pretty good one. I've diagnosed temperature problems (grab ice from the freezer, apply to chip, see it work...), clocking problems (you inser

Interference is a pretty good one. I've diagnosed temperature problems (grab ice from the freezer, apply to chip, see it work...), clocking problems (you insert strategic delays, sometimes on the order of thousands of instructions) and just badly documented registers (make sure mystery bit number 13 gets toggled just right, or it's curtains). It's fun stuff.