Oh my fuck are my fingertips burning right now.
I've seeded more jalapeno peppers than I could count in one day and have developed a trick to do it quickly and easily.
1. Find a piece of silverware with a thin handle that has a curve running down the length of the handle. Not a curve down the length of the handle but if it has that no problem but a curve over the width. If you don't have one you can find one at the Salvation Army or steal one from a restaurant. It's cheap silverware.
2. Cut the end off the pepper.
3. Push your curved silverware handle down the pepper and spin it around. It will disconnect all the pith and seeds from the body of the pepper after you get the technique down.
4. Pull all those guts out when you extract the handle. You may want to tap the pepper out to get all the seeds.
I've taught a dozen cooks this trick, and I'm sure that they have taught a dozen more. It's the fastest easiest way to gut a jalapeno.