Just a little repeating trick I made up a couple of days ago. All it is is a few mounts and transitions thrown together, nothing revolutionary, but done right it looks pretty good.
1. Throw a houdini mount.
2. Roll the yoyo off around your non-throwhand middle finger, and under mount it.
2.5 As you do this, drop the string from your throwhand index finger and let the yoyo swing round.
(You should now be in an under mount around your middle finger)
3. As the yoyo swings up to your throw hand, cut into the single string closest to you (with your index finger) and hold the loop. The yoyo should fall out of it.
4. Swing the yoyo back over your non-throwhand index finger and mount it on the front string.
5. Drop the string from your throwhand index finger.
(You should now be in a trapeze on your non-throwhand index finger, with the string coming over and around your middle finger)
6. Swing the yoyo in the same direction over your non-throwhand and catch the string closest to you on your throwhand index finger.
(You should now be in a double or nothing)
7. Throw the yoyo off the string and over your throwhand index finger
8. Mount the yoyo back on its own string.
(There will be a loop around your finger)
9. Drop the string from your non-throwhand index finger.
(You will be in a mount resembling a 1.5 but with a twist in the string)
10. Roll the yoyo over your throw hand into a man and his brother mount
11. Roll the yoyo off the string in the opposite direction all the way around and back into a houdini
(The string may loop around your throwhand index finger as you roll over into the houdini mount. Tilt it down slightly to prevent this)
Phew. Long description for such a short combo!
Remember, these are all fluid motions and should flow into one another. Keep practicing till you have the trick looking smooth. Smoothly performed tricks look 100x better than jerky ones ;)