I'm not sure what this tiny (less than 1 inch long) fellow is, but he appears to be some type of young goby, and the fact that he is showing a large dorsal fin (as a warning to the big creature taking his photo) suggests that he, too has some venom in that spine...
Unusually colored cockatoo waspfish (4-5 in. long) - most of them are dark brown.
Rhinopeas scorpionfish (8-10 inches)
