Nudibranch nudibranch nudibranch nudibranch!
Nudibranchs are all carnivores. Most of them (all of them, if in too dense an area) are cannibalistic. Some of these very cool/scary invertebrates even actively hunt down Portuguese Man o' Wars for food...you know, the ones that have the second most painful sting of any sea creatures? Yeah, they eat those, and take the nematocysts that make up the tentacles for their own protection.
Proceedings of the General Meetings for Scientific Business of the Zoological Society of London. 1906.