Bubble

Shoot at an enemy to trap him inside a bubble which floats into the sky before popping and dropping the enemy back down to the ground.

The more you use this, the longer the bubble lasts, and maybe the larger the bubble gets to trap bigger enemies

Maybe it should be possible to control the bubble, so you can set enemies down where ever you want. At first you can control the bubble as you fire it so you could, for example, fire it upward and around a corner, hitting the enemy. Then later you could control it even while the enemy is inside of it.