I recall a machine which you had a pencil which was connected to a wire, you would use the pencil to scribble on a pad, and then the pencil became a musical instrument . the heavier the mark the different the sound. I do not know what it was called, but I remember hours playing with this, drove my mum and dad crazy. I think they put it away (or threw it away) cause it was a bit irritating as I remember.
Another toy I grew up with was the six million dollar man "action figure." and with the roll up skin to show the bionic parts. I lost the parts, so I took playdough, and pressed it in, and took some wires and stuck it into the playdoough so that I could pretend to be operating on his arm. LOL