Boing-E-Boing is a cool trick for the yo-yo. It is fairly simple, but still looks very amazing.
First, go into a split bottom mount. To do this, throw a sleeper and go into a brain twister mount, but instead of bringing you throw hand under the yo-yo, swing the yo-yo over your index finger of your throw hand and it lands on the string. That is a split bottom mount.
After the split bottom mount is in place, pass the yo-yo forward once by switching your arms.
Now the yo-yo is in the middle of two strings. Move your index finger at the top up and down. Watch as the yo-yo bounces between the two strings because it has nowhere else to go!