Why and how can the player use a full sized bow/arrow inside a narrow vent-duct? It obviously wouldnt be possible or fit.
I wish that surrounding environment would act to limit certain weapons/methods.
Narrow ducts or spaces should stop users equipping a bow, rocket launcher or assault rifle (restricting to hands only, or pistols)
Water could make some guns temporarily break if you equip them in wet- areas or under-water. A drying time could be introduced before they work again.
Stuff like that...it brings a touch of metal gear solid into it IMO, adds realism and REALLY makes people think about what "path" they want to chose based on what weapons could be suitable for the terrain and environment.