The cheapest are those twist flint lantern ignitors. They create a shower of sparks, but you need to replace the flint every few hundred shots.
The ultimate ignition system can be found at http://www.aaroncake.net/spuds/mods.htm . Look for the high voltage ignition system. About $15 to make, but will get the job done every time.
aaron do you not think that it is a bit dangerous putting 10,000 volts at one amp through a non insulated circuit. ps are electric fence circuits any good
HAS EVERYONE FORGOTTEN ABOUT RELAYS!!!!!! wire a relay like a buzzer. it will pulse power through a ignition coil!!. costs much less probably only 3 to 5 dollars. much better than &15.00!!!