How do you use the one-shot orb on Pokemon Mystery Dungeon red?

Answer 1

easy. you go up to the foe and use it. if you want to use it on a boss like gengar or zapdos, you can't.

here are other items or moves not able to be used...

rock smash

blast seeds------------- they are really weak, but usable.

any orbs

hms

dive-- unless you are on water

and, if you are on water, dig.