I found two Thelenota rubralineata, Candy-Cane sea cucumber, over the weekend. Not sure if these ever make it into the trade, since they live pretty deep, but I thought they were pretty cool looking.
We had a few of these years ago in the Solomon Islands. We called them Pineapple cucumbers and sold them right away. I don't know the story of how deep they were collected or of how they fared with aquarium life.