Ctenophores are so far almost completely unknown within Homeopathy, with only my own trituration proving existing. As such 
a proving of any Ctenophore would be a very useful addition to the Homeopathic materia medica. Since my trituration was of a Tenticulata, a proving of a member of the Nuda would be the best use of effort.
One interesting species of Ctenophores for proving would be Haeckelia rubra, a species which capture the cnidocytes of Ctenophores. Due to their unusual benthic and symbiotic lifestyle and wormlike bodies, members of the Platyctenida would also be excellent candidates for proving.
Image Credit: https://commons.wikimedia.org/wiki/File:LightRefractsOf_comb-rows_of_ctenophore_Mertensia_ovum.jpg