I'd love for a mod like this to be released. Where you have an item you can use like a laser or "paint" the target and after a few moments a missile/nuke comes down and blows it up. I know they have a meteor mod that works kind of the same way, but instead of obsidian you could just use tnt. It'd be like a portable TnT cannon you can aim anywhere.
you could make a missile silo item that fires a missile straight up. when the missile has traveled a certain distance up it would try to find a designated area. the missile could hit a designated chunk that either had another block or item in, or in SMP another player that was designated as an enemy. if no target is found the missile could go a few chunks away from the launcher and fall to earth. you would right click the launcher to launch, and click it again to detonate the missile in mid flight. this would require a item to launch the missile, a designating block and a way of getting the block to the enemy base without being detected - a bazooka type launcher? the explosion would have something like the power of TNT times ten. have another type that penetrates the ground an then explodes.