This instructable is two videos that will show you how to make a self cocking crossbow pistol from scratch. It is a fun project that involves melting and pouring aluminum (don't worry, it's easy), PVC bow making, and some work with small simple mechanisms. Depending on what skills you already have this could be a good learning project. It will involve some work and some sort of difficult steps but it is still within reach of the complete beginner.
Everything that really needs to be said is said in the videos, so here they are. I hope you get something useful out of this instructable and have a good time doing it:
Instructional video part 1:
Instructional video part 2: