Mega Heal Bomb is an alternate ability for the Scientist's Sticky Explody Ball. It does not hurt plants. It will explode after 3.5 seconds when deployed. When it explodes, it will heal all zombies in its radius by 50 health. Like most of the other alternate abilities, it was introduced in the Garden Variety DLC. It takes 15 seconds for it to recharge.
The Mega Heal Bomb is always popular at parties. Just roll it into a group of friends and watch their health replenish before your eyes!
The Mega Heal Bomb is good for three things; first, it is good for patching up groups of zombies that have all gotten a little banged up, second, it is good for giving singular zombies a quick health boost instead of deploying the Zombie Heal Station (and then being forced to wait for 45 seconds for it to become usable again), and finally, the Mega Heal Bomb is also good for personal healing when far away from others (this allows you to save the Zombie Heal Station for your teammates) and if you're using the Heal Beam of Science, which restricts personal healing. The only downside to the Mega Heal Bomb is the amount it heals. The Zombie Heal Station and Armored Heal Station can both heal more than the Mega Heal Bomb, in exchange for other qualities.
Do not be afraid to deploy the Mega Heal Bomb near groups of injured zombies. If they see it coming, it should attract everyone who wants healing. If there's a Peashooter or Kernel Corn nearby, you might want to wait as they could deploy their abilities and vanquish everyone.