A simple mod that does exactly one thing: Give you lifesteal when you're using a berserk pack.
While your player has a PowerStrength item in their inventory, every time you do damage to something within a 128-unit radius, you heal 1 HP. It's That Simple[tm].
It'll apply to any damage you do while zerked, as long as you're close enough to the target. Strictly speaking, you could run right into a crowd of zombies and fire a rocket-launcher point blank, and if you survive the initial blast, you might actually gain health from it.
This could be cheesable with things like the chaingun or chainsaw, but I'm okay with that. The whole point of doing this is to incentivize players to actually use berserk for the thing it was intended for: getting in there and being Too Angry To Die.
This probably means that the Berserk effect of whatever mod you're using is not implemented with the PowerStrength item, for whatever reason. For instance, Nobody Told Me About iD uses its own special item to make berserk also give extra movement speed. If you find something that doesn't have lifesteal, even when you've got the berserk effect on and you're right up in their face, please open an issue with a link to where you found the mod in question and explain which item isn't zerking the way you expected. I'll see what I can do about it.