I have seen a Minecraft mod called the Lucky Block mod, and it does some pretty awesome stuff. It only adds one thing to the game, and that is the lucky block. You can place that, and when you destroy it something random will happen. There are TONS of possibilities, like giant explosions, charged creepers, getting trapped in a cage, random loot, and much more. I decided to make this in Bukkit, and because all of the possibilities in the mod are all vanilla things, I can easily do it in Bukkit. I have already gotten a few things, too.