The ocellated icefish you see above has a very unique blood: it's totally transparent. Discovery News tells us:
The reason, say experts at Tokyo Sea Life Park, is that the Ocellated Ice Fish has no hemoglobin, making it unique among vertebrates the world over.
Hemoglobin is the protein found in every other animal with bones. It is what makes blood red and is the agent that carries oxygen around the body. [...]
Researchers believe the fish can live without hemoglobin because it has a large heart and uses blood plasma to circulate oxygen throughout its body.