First off, welcome to the forums! :D
But, there is already a pulser as Alka said and it's so powerful that players can't use it. And, if granite was to be obsidian, the block is already used to place a cannon. If you meant gravel, that could work. However, on the more positive side, it does sound like a fun weapon and I'd definitely use it a bit but it might kill you. Plus, it might be practical to place near a lot of enemies, jump on top of, and get a lot of them. I do see its use, but it's not my decision obviously. Good idea I think, though :)