AgentVoxel and I participated in ludum dare 27 and make 10 Second Destruction. A game in which you point and click around a city with 10 seconds and try to destroy as much as you can while getting score. The game currently looks like this

[attachment=18033:bandicam 2013-08-26 15-18-38-687.jpg]

We have levels and score and need suggestions if anyone has a suggestion of something to add please put it in the comments.

Thanks.

-Integershift

If you want to see more of the game here is a youtube link

How about creating destruction chains with a score multiplier?

Exploding a gas station for example would have a massive blast radius and take out a lot more objects in the area. It could start fires which could in turn create even more destruction.

Seems like you could get some inspiration from good old Crash Junction: