I will start...for me, not really a toy but in the same sort of vein -
feedback. To control this in pitch and fit 'musically' into a song is
For me I think it is thimbles...
Of course inspired by Mr. Ron Thal, but the technique is more than just a 'trick'. It can be very useful!
I'm not a big effects guy, but reverse delay can make some funny sounds. But the real challenge is to make the guitar sound like it has reverse delay without actually having it!