Apparently Viking Beserkers would take hallucinogens before going into battle.
What would you take before slaughtering a bunch of kill crazed shambling zed?
FWIW, the Amanita muscaria was supposed to give a real energy boost but also cause crazy mood swings that probably wouldn't work well in a battle.
The CIA, of course, experimented with LSD & that didn't fly.
So, your choice?