Concept art:
Find the dead birds hidden in various locations to unlock concept art. Note: To find the birds easily, listen for the sound of flies. That sound indicates that a dead bird is near.
Sprinting:
Sprinting is not that useful on stairs. Save it for level surfaces.
Guns:
As with all guns, it is best to save the revolver for fights against multiple enemies (or against exceptionally tough loners). Particularly weak enemies can be finished off with a combination of Taser and kicks instead.
Check the recycling bins. There are weapons in almost all of them.
Strategic dropping:
Drop important weapons and tools near distinctive objects or in easy-to-find spots. By doing this, you will not have to search for them later.
Big melee weapons:
If you want to use big melee weapons, practice hanging back, then veering ahead far enough to hit your enemy with your weapon. Then, drift back. This makes the most of your weapons’ superior reach and keeps you away from your opponents’ faster weapons.