1 nutcracker, hand held
1 vise grip (optional)
You hold the macadamia nut with the nutcracker or vise grip, rest it on a hard surface, and hit it with the hammer. I didn’t have to hit that hard, I think.
A Macadamia nut shell is hard so normal nutcrackers usually can’t open them or you have to get an expensive nutcracker for opening the nut. When i just used the hammer the macadamia nut bounced all over the room and still stayed intact. This is an inexpensive way to open them with common household tools, I think.