factorio
The other day, while playing Factorio (0.15.38) I damaged a tree with a grenade. It was almost destroyed, had red health boxes. I went to chop down several other trees and when I got to this one, the health boxes were yellow.
Do trees regenerate after taking combat damage, like the player does?
Do biters, and/or biter nests?
You can use your weapons to clear them out. Early on, shotgun fire and grenades are significantly faster than cutting them down by hand.
Regular rockets do their 60 damage to a single target. Explosive rockets do 40 damage to everything in a circle centered on the target (there is no falloff). While this allows doing much more total damage, it can hit things you don't want to hit, and is not more effective against a single enemy.
The pictured test (current “stable” version, 0.10.12) shows that that the radius of the explosion is apparently 6 tiles. All of the pipe sections took exactly 40 damage.
(Note that unlike the shotgun, rockets cannot be fired in an arbitrary direction; you must target an object.)
Best Answer
From personal experience, things do heal after being damaged some (trees, biters, biter nests, etc). The only things that don't are structures. Those you have to repair.