Before your monkey brain goes all Rambo and you conclude that the only means to open a husked coconut is with a machete or gun, try something a little safer. There are two methods that won't endanger you from losing a thumb nor will have your neighbors up on arms for blasting rounds in your backyard.
These methods require you to drain the coconut first. The water from this hard-cased fruit is full of electrolytes and perfect for rehydration after strenuous physical activity.
There are three "eyes" or soft spots at the end of a coconut. Find the softest one and puncture it using the screwdriver or metal skewer. Once you have created a sufficient hole, turn the coconut upside down and set it atop of the glass so the water can drain. This will take several minutes and you may want to give it a good couple of shakes to get the last drop. In the end, you will garner ½ - ¾ cup of juice.
This method uses modern amenities to help ease the oomph needed to open a coconut.
Even though you are working with a coconut that hasn't been split in the oven beforehand, it is still a straightforward and simple process.
Don't let your friends know how easy it is to open a coconut; Let them believe you've really earned that pina colada!