For me it's the Pike Blenny, one of my favorite fish I ever had. Would pay a pretty penny to get another one if anyone collected them, unfortunately no one does. It's from the tube blenny family.
Picture of the one I had is in my Avatar (OrangeThroat Pike Blenny)
Cool fish lots of personality, would display by puffing out his gills if felt threatened, would live in a cocoworm tunnel or SeaFan tube. Apparently not that rare, just not collected often.
Some one jsut asked me about these. They used to collect them in the Sea of Cortez and they'll be showing up again shortly..
Here's mine from 8 or so years ago...