DOOM: 10 Things You Didn't Know You Could Do

7. Let Enemies Fight Each Other Instead

I only discovered this in Hell, but actually holding back as you progress through the environment means you'll stumble upon the occasional firefight happening between enemies, rather than them teaming up to take you down.

There's probably some lore-based reason as to why everything isn't copacetic down in Hell, but feel free to let battles play out, let the ranks thin a little and then wade in to mop up the survivors - who will then be on less health to boot.