I haven't done too much hybridization, but some of the ones I have done have turned out pretty good...
I've mixed caramel and/or vanilla into some of my
tobacco flavors to effectively create an RY4 effect (I can imagine adding other flavors like black cherry, blueberry, grape, etc. could be equally as enjoyable instead of the caramel and vanilla).
I've added vanilla to root beer and that turned out tasting a little like a root beer float.
I've also taken gummi bear, pineapple, grape jolly rancher, cherry, and hawaiian punch and mixed those together to get a Frankenstein punch thing going on, which was actually pretty pleasant.