The Placer and the Breaker

In the placer you place a random block and when it is powered up it randomly places one of the blocks inside it (just like a dispenser). In the breaker you place a tool, like a pickaxe. And then when there is a block in front of it and you power it up it will break it with the tool inside it. If it tries to break cobblestone with an axe you just don't get the block. If it breaks cobblestone with a pickaxe you do get the item. For every time you break a block the durability of the tool inside it goes down of course! :)