An automotive ignition coil (especially a performance
one) will be able to give you a lot more punch than a TV
flyback, though at greater volume / weight.
You need a switch device that can stand being avalanched
if the load doesn't take the current as expected. The breakdown
of the switch device can limit the output voltage, TV flyback
transistors are very high breakdown and usually pretty
low beta as a result, so be sure the PIC output is not also
a limiter (starving the switch device).
Why do you need a microcontroller to make an arc?