The Flip Hole for sure! This is the first masturbator my husband has ever tried. It seems to be a hit. Since I am the one cleaning it, I appreciate that it opens for easy cleaning; all the texture is amazing! No toy of mine has that much texture.
While I was cleaning it the other day, my fingers were slipping gently in and out of the grooves, over the ridges and bumps. I guess my eyes were closed while I was doing this. My husband had come into the doorway and was watching me. I was startled by his voice, when he asked me if I was OK. I told him, "Yes, I was daydreaming. Just imagining what this feels like when you put your cock in it."
There is only one other toy I have seen that makes me wish I had a dick for a day.