1 Terry: Actually, Steve, sharks are cartilaginous fish. They have gills. They're not even remotely similar to reptiles.
2 Steve: Crikey! But if one 'as me hand, and I shove me arm further down 'is throat, will 'e let go?
3 Terry: Um... maybe...
4 Steve: Close enough!

Cartilaginous fish also include the skates and rays. But if you really want something weird, check out the picture of the Pacific spookfish.

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2015-01-12 Rerun commentary: Alas the Wikipedia page I linked to for the picture of the Pacific spookfish no longer has a picture of that fish on it. Here's one from the Australian Museum.

Which is a very cool museum, by the way, in my home city of Sydney. Despite the name, it's a natural history museum, not a museum about Australia. It is located in the heart of the city, facing Hyde Park, and gives its name to a nearby underground railway station.