This is an air pressure gun which I made from some junk which was kept in my house and was useless . it would approximately cost about 100 rupees or 1.68 us dollar. It is very simple to make.
Step 1: Materials
First collect these materials
A water valve
Step 2: Putting the Pin in the Bottle
Make a hole in the bottle and put the pin it and then use a hot glue gun to fix it
Take the pipe and connect it to the valve
The last step is to connect the bottle to the other end of the valve