Like notch wanted to implement in the game if an admin does /bowboom on it will enable shooting tnt through arrows. When they do /bowboom off it will disable that. Permissions: bowboom.use (default op)
Do you really need that ? I mean there is a lot of different plugins which allow you to use explosive arrow, just one who cross my mind : CraftArrows. Good luck.
I'll do this, just in case you don't want to use CraftArrows. Edit.: Here you go. I haven't tested it so tell me if it works: https://mega.co.nz/#!5IdC2Qrb!H52aEGTplrA0QaiZ_A7zdw7pLV5cjhZPKMoGe9odkSk.