Julian K. Finn (Victoria Museum, Australia), Tom Tregenza (University of Exeter, UK), and Mark D. Norman (Victoria Museum, Australia) have found that invertrabae can show cognitive sophistication by filming octopuses using a tool. Here are the summary of the paper, videos about the phenomenon, and a link to the fullpaper.
"The use of tools has become a benchmark for cognitive sophistication. Originally regarded as a defining feature of our species, tool-use behaviours have subsequently been revealed in other primates and a growing spectrum of mammals and birds. Among invertebrates, however, the acquisition of items that are deployed later has not previously been reported. We repeatedly observed soft-sediment dwelling octopuses carrying around coconut shell halves, assembling them as a shelter only when needed. Whilst being carried, the shells offer no protection and place a requirement on the carrier to use a novel and cumbersome form of locomotion — ‘stilt-walking’."
As it is shown in the videos (see at the end of the post), they are one-coconut-carrying and two-coconuts-carrying octopuses. Instance of coconut's use is : sheltering against unknown intruder in the field (the octopus flees in the half of the empty coconut to escape the human observer).
Another video on the BBC website (with commentaries about the paper and remarks by biologists, including the authors of the paper) : Octopus snatches coconut and runs.
Other videos can be found on Current Biology, in the online version of the paper : Julian K. Finn1, Tom Tregenza, and Mark D. Norman, "Defensive tool use in a coconut-carrying octopus", Current Biology, Volume 19, Issue 23, R1069-R1070, 15 December 2009. (Full-text.)