Pop-Up Walls! A unique trap
First of all, I didn't think of this myself. I saw the general idea in another thread with about 9 other suggestions and since the grammar is sloppy and the thread is long, I figured few people would get around to reading it. But I do think it is a great idea. Now...
Unlocked at TH 8, these walls at first seem like ordinary walls. They cost the same, look the same (actually, these will have to look different so you can differentiate between the two types, just haven't thought of it yet), and have the same upgrades. But! They aren't just walls, they're pop-up walls! The deal is, just like traps, they are invisible to the enemy until they get within one tile of them, and all of a sudden they pop out of the ground! Troops wouldn't know they are there just like you, so if there is a cannon just inside a row of pop-up walls they'll try to go get it, only to be stopped! Wallbreakers will not target them until they appear, of course, and all that...
You unlock 10 at TH 8, another 10 at TH 9, and finally 5 more at TH 10.
Unlike damage-dealing traps, these do not need to be re-armed, like regular walls.
I think these walls would make base designs even more interesting and add some surprise and strategy to the game.
What do you think?